sulfur lab response sheet. name: partner: q1: what shape ... · sulfur lab response sheet. name:...
TRANSCRIPT
Sulfur Lab Response sheet. Name: _____________ Partner: _____________
As you go through the power point and do the lab, stop and answer questions here first. After you have put down your best guess, correct them if necessary. This sheet will then prove very useful for the quia follow-up questions.
Q1: What shape do these S8 molecules have? __________________
Q2: Each sulfur has two sulfur atoms bonded to it, but what else does it have? __________________
Q3: So with two bonds and two ghosts (AX2E2), what bond angle would you predict? ________________
Q4: What is the interior angle of an octagon (angle q in the diagram at right)? ________
Q5: So the question is: How can the sulfur bond angles all be 108°, but they form an octagonal
ring, and the interior angles for an octagon are all 135°? ______________________________
Q6: When you built the model of the S8 ring, What did you discover?
_____________________________________________________________________________
Q7: Try to figure out the very best arrangement for the atoms in this puckered octagonal arrangement. Draw it below.
Q8: How do you think the allotropes are different? __________________________________
Q9: Which allotrope appears to be more densely packed? ____________
Q10: What evidence is there in the phase diagram that rhombic is more dense?
Q11: Which allotrope is more stable at normal room conditions? _______________
Q12: What do you think the rhombic crystals look like?
Q14: Is sulfur polar or nonpolar? __________________
Q15: Why are we interested in whether sulfur is polar or not? _______________________________________________
Q16: Would sulfur dissolve better in: a polar solvent or a nonpolar one? ____________
Q17: Which of the following would be a good solvent for sulfur:
Q13: What did the sulfur powder
look like at 100X magnification?
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Q18: Draw the recrystallizing sulfur at 100X mag
Q19: How do you think you might convert rhombic sulfur into monoclinic? _____________________________________
Q20: What else might you do to convert to rhombic sulfur into monoclinic? ____________________________________
Q21: Draw what you see in the filter paper for the monoclinic sulfur crystals:
Q22: When the sulfur powder melted, what was going on at the molecular level to the S8 rings?
______________________________________________________________________________________
Q23: What are the little black dots on the ends of the S8 chains? ______________________
Q24: Unpaired electrons tend to absorb visible light. What effect do you think that will have on the liquid sulfur?
_______________________________________________________________________________________
Q25: What do you think the S8 chains with will do? _______________________________________________
Q26: What do you think will happen to the liquid’s viscosity as it polymerizes? __________________________
Q27: If the very viscous mass of long-chained sulfur molecules is heated even further, what do you think might happen?
__________________________________________________________________________________________
Q28: What effect do you think cracking will have on the color of the liquid? _____________________________
Q29: And what do you think will happen to the viscosity of the sulfur liquid during cracking? ___________________
Q30: Do you think the random mixture of sulfur chains of varying lengths will arrange themselves in a precise crystalline
pattern? _______
Q31: Explain your answer for Q30: ____________________________________________________________________
Q32: What two other substances from previous labs were referred to as amorphous solids? __________ __________
Q33: What are some of amorphous sulfur’s physical properties? ___________________________________________
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Nuclear Reactions Tutorial Note sheet Name: ________________________
As you go through the power-point tutorial, every time you come across a (Q1) or (Q2), stop and answer that question
on this sheet. Don’t worry about whether it’s right or wrong, just make your best guess. Then when you return to the
tutorial and discover the correct answer, go back and fix your original answer, but do not erase. Just draw a line through
what you had written (if it was wrong), and write the correct response after it. If your first response was correct, just go
back and put a check mark (√) in front of it. For example:
QX: What is the capital of Connecticut? Connecticut City Hartford QY: How is element #9 spelled? √ fluorine
Q1: Why is this reaction impossible to balance? _____________________________________________________
Q2: What are the two particles that make up the nucleus? __________________ __________________
Q3: In the format known as isotopic notation: , the 56 is called the __________________ number and it
indicates the ________________________________
Q4: In the format known as isotopic notation: , the 137 is called the __________________ number and it
indicates the ________________________________
Q5: So how many protons _____ and neutrons _____ are there in a nucleus and how many protons ____ and
how many neutrons _____ are there in a ?
Q6: What would be the isotopic notation (like ) for an alpha particle?________
Q7: What do you think the U-235 would decay into? ____ +
Q8: What particle do you think is produced when C-14 decays into N-14? + _____
Q9: What is the neutron : proton ratio in a nucleus? ________ What is the n:p ratio in a nucleus? _______
Q10: How can you tell at a glance that this is not a decay reaction? _______________________________________
Q11: What are the mass _________ and charge ___________ of a neutron?
Q12: What particle is produced in this reaction? + ____
Q13: What particle is produced when B-8 undergoes electron capture? + _____
Q14: How can you tell this is neither a decay nor a capture reaction? __________________________________
Q15: What particle is ejected when an O-16 nucleus
is bombarded with a neutron and changes into a N-16 nucleus? ? + + _____
Q16: What is the name of this type of reaction in which an atom is split? _____________________
Q17: What would be produced in this fission reaction? + + ______ + 3
Q18: T or F: The splitting of a nucleus like this releases enormous amount of energy and can result in a huge explosion and massive devastation.
Q19: How many times have fission bombs (atom bombs)
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been used in warfare and which by which nation(s)? * _____ ___________________________
Q20: What do you think is the significance of the high speed neutrons that are produced? _________________________
Q21: The minimum amount of fissionable material necessary to allow a chain reaction is referred to as ______________
* = not answered in the tutorial, but easily researched
Q22: What is the problem with the “daughter isotopes” produced in a fission reaction? __________________________
Q23: What is the name of this type of reaction in which two small nuclei are fused together? ______________
Q24: What is produced by this reaction? + _____
Q25: Why do fusion reactions require such high energies (high temperatures)? _________________________________
Q26: Why do you think we have not been able yet to harness fusion reactions for use in nuclear power plant? ____________________________________________________ Q27: Identify each of the following reactions as a decay, absorption, bombardment, fission of fusion reaction.
Q28: Find the three mistakes in the reactions above.
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Nuclear Reactions WS Name: ___________________ Complete each of the following nuclear reactions by determining the missing particle; then identify the type of reaction (alpha decay (1), beta decay (3), positron decay (1), electron capture (1), absorption (2), bombardment (5), fission (2), or fusion (2)). The first two are done for you.
1) + + _______________
2) + _______________
3) + _______________
4) + _______________
5) + _______________
6) + + _______________
7) + + _______________
8) + _______________
9) + _______________
10) + _______________
11) + _______________
12) + _______________
13) + + _______________
14) + + _______________
15) + _______________
16) + + + 5 _______________
17) + + + _______________
For 18 - 22, write the nuclear reaction that matches the description. Also fill in any blanks.
18) A lead-214 nucleus changes into a bismuth-____
nucleus as it undergoes beta decay.
19) Gold-196 is bombarded with a _____ producing
platinum-193 with an alpha particle ejected
20) Two lithium-6 nuclei fuse together to form
a nucleus of _______________
21) Uranium-235 is struck by a neutron, splitting it
into barium-144 & krypton-89 (& ___ neutrons)
22) An electron is captured by a
sodium-21 nucleus, producing ___________.
Some particles frequently involved in nuclear reactions:
symbol name
or alpha particle (a helium nucleus)
or beta particle (an electron)
positron (a positive electron?)
neutron
proton (a hydrogen, H-1 nucleus)
deuteron (a deuterium, H-2 nucleus)
gamma ray (not really a particle, but very high energy light)
Ans (IRO+ extras): -1 0 0 0 0 0 1 1 1 1 1 1 2 2 3 3 4 4 6 6 7 10 12 12 13 13 14 21 24 26 27 29 48 50 65 81 83 84 91 93 112 136 206 218 220 230 238 e e n n n Al Al Bi C Cd Cu H He He Li Mg N Ne Np P Pa Po Sn Tl proton
23) What particle is produced when an At-224 atom undergoes alpha decay? ____ 24) What particle is produced when silver-112 undergoes positron absorption?____ 25) What particle is produced when a U-238 atom undergoes a series of two alpha-decays and three beta-decays?____
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bombardment
beta decay
Each of the following seven pictures corresponds to one of the five nuclear reactions type – some of the types are used more than once. For each picture, indicate which type (fusion, fission, decay, bombardment or absorption) you think it best matches up with; then explain why it matches up with that type, and then write it as a reaction. If there are any shortcomings of the analogy, list them. For example, if a picture showed a hungry boy eating a hamburger, this might be absorption, because the boy is absorbing the hamburger, the reaction: hungry boy + hamburger satisfied boy. One shortcoming might be that the burger was eaten gradually in bites
instead of all at once.
Type: ______________ because: ___________________________________
Reaction: ______________________________________________________
Shortcomings: __________________________________________________
Type: ______________ because: ___________________________________
Reaction: ______________________________________________________
Shortcomings: __________________________________________________
Type: ______________ because: ___________________________________
Reaction: ______________________________________________________
Shortcomings: __________________________________________________
Type: ______________ because: ___________________________________
Reaction: ______________________________________________________
Shortcomings: __________________________________________________
Type: ______________ because: ___________________________________
Reaction: ______________________________________________________
Shortcomings: __________________________________________________
Type: ______________ because: ___________________________________
Reaction: ______________________________________________________
Shortcomings: __________________________________________________
Type: ______________ because: ___________________________________
Reaction: ______________________________________________________
Shortcomings: __________________________________________________
1.
2.
3.
4.
5.
6.
7.
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Half-life WS log = Name: _______________
For problems 1-5 below, do not use the above equation: just think it out based on the fact that the sample is being cut in half every half-life. Then for 6-10, approximate your answer first, then set up & solve using the log equation above. 1. How long would it take for a 80.0 mCi sample of H-3 to decay down to just…
a) 40.0 mCi? _______ b) 20.0 mCi? _______ c) 1.25 mCi? _______
2. Of a 32.0 mCi sample of I-131, how much will remain after…
a) 16 days? _______ b) 40.0 days? _______ c) 80.0 days? _________
3. a) What percent of a Co-60 sample will remain after 10.52 years? ______
b) What percent of a Na-24 sample will decay in 45 hours? ________
4. Currently a Ba-137m sample has a radioactivity level of 0.350 mCi. What was its radioactivity level…
a) 2.6 min ago? _______ b) 10.4 min ago? ________ c) 20.8 min ago? ________
5. a) A sample of Ga-74 decays from 24.0 mCi down to 1.5 mCi in a period of 32.4 min. What is Ga-74’s half-life? _______
b) A sample of Mg-28 decays down to just 25% of its original level in 42 hours. What is Mg-28’s half-life? ________
c) It takes 7.5 days for 96.875% of a sample of Kr-79 to decay. What is Kr-79’s half-life? ________
For the remaining problems, first approximate the answer using the same technique used above, then set up and solve using the log equation. Remember to show your work. 6. How long would it take for a 80.0 mCi sample of H-3 to decay down to a) 23.0 mCi? _______ b) 68.0 mCi? _______
Est: _______ Est: _______
Half lives of some radioisotopes: H-3 12.3 y C-14 5730 y Ba-137m 2.6 m U-238 4.5 billion y Co-60 5.26 y Po-215 1.8 ms Na-24 15 h
I-131 8.0 d
N0 Nt
0.301 t t½
Ans: (IAO +1): 0.03125 0.443 0.700 1.0 1.36 1.5 2.88 3.38 4.43 5.6 8.0 8.1 9.34 12.3 14.2 21 22.1 24.6 25 31.7 52.5 73.8 81.1 87.5 89.6 Units: (IAO +1) min min hr hr day day yr yr yr yr yr yr yr % % % % mCi mCi mCi mCi mCi mCi mCi mCi mCi mCi
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7. Of a 32.0 mCi sample of I-131, how much will remain after a) 9.4 days? _________ b) 22.8 days? _________
Est: ________ Est: ________
8. a) What percent of a Co-60 sample will remain after 4.89 years? ________
Est: _________
b) What percent of a Na-24 sample will decay in 36 hours? ___________
Est: _________
9. A Ba-137m sample has a level of 0.350 mCi. What was its level…a) 5.1 min ago? _________ b) 53 sec ago? ________
Est: ________ Est: ________
10. a) A sample of Pb-201 decays from 24.0 mCi down to 10.0 mCi in a period of 11.8 h. Pb-201 half-life =_________
Est: ________
b) It takes 7.50 min for 78.5% of a sample of Ne-24 to decay. What is Ne-24’s half-life? _________
Est: ________
11. Now make up your own half-life problem for which the answer is the left-over number & unit from the answer box.
Now solve it in the space below.
Ans: _________
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HALF-LIFE LAB FLIPPING BEADS! Name: _____________ Partner: ______________ The following activity is designed to illustrate how radioactive decay is all a matter of chance. Just because a nucleus is unstable, it does not mean it will decay immediately into something else. It only means there is a chance of it decaying in a given time period. Some nuclei are more unstable than others, and so the chance of them decaying is greater. The most common way of referring to this decay rate is in terms of something called the “half-life” of a radioactive substance. A half-life is the period of time over which there is a 50-50 chance of a nucleus decaying. The shorter the half-life, the more unstable the nucleus is. Cobalt-60, for example, is a radioactive isotope with a half-life of 5 years. That means, over a 5 year period, chances are 50-50 that any given nucleus of Co-60 will decay. It is conceivable that in a sample containing just forty cobalt-60 nuclei, that none of them will decay over a five year period, but it would be rather unlikely, just as it would be rather unlikely to toss 40 coins up and have them all come up heads. Chances are, about half of the nuclei will decay (which is why they call it a “half-life”). When you consider a sample containing 40 trillion cobalt-60 nuclei, the chances that none will decay during a half-life is extremely small. With such a large sample size, the chances are much greater that what happens will match the odds of it happening. This is sometimes referred to as the “law of averages.” Procedure: 1. Place 40 straw section “beads” on their sides in the box. These should look like ’s when viewed from above, and they represent atoms of the radioactive element “sidium” -- they are unstable but we will pretend they are somehow frozen in time and have not had an opportunity yet to decay! 2. Cover the box and shake thoroughly. This shaking will represent the passage of 1 year. As you shake, some of the beads will tip over onto their bases (and look like ’s when viewed from above). These represent the element “basium” that sidium has decayed into. Before looking, make a guess as to how many atoms you think will remain as un-decayed sidium [Guess = ____]. Then, open the box and see how close you were. Remove all the basium atoms ( ) and place them in the bag. In the upper left-hand corner of the table below, record how many sidium atoms ( ) remained in your box after this first shaking. 3. Do not put the removed basium atoms back into the box. Again, cover and shake -- just those sidium atoms left in the box, and guess how many will be left un-decayed this time [Guess = ____]. Again, uncover, remove all the basium atoms ( ). In the table below, record how many ’s are left in the box. 4. Repeat this procedure until all the ’s atoms have decayed. Make sure you are shaking the box thoroughly each time! When you have finished, go to the computer and enter your group’s results. 5. Now get a different sample bag, this time of “shortium” atoms, and repeat steps 1-4 with them. 6. Graph your results. Use x’s to plot points for the number of sidium atoms remaining (on the y-axis) versus time (in
years*) on the x-axis on the graph paper provided. Then, on the same graph, use ’s to plot the pooled class data. Also, on the same graph, use o’s to plot your data for shortium atoms, and then use •’s to plot the class averages for shortium. Draw best fit lines only for the pooled class data for both sidium and shortium decay. Data Table: Number of atoms remaining after... (*Assume each shaking represents the passage of 1 year.)
0 yr
1 yr
2 yr
3 yr
4 yr
5 yr
6 yr
7 yr
8 yr
9 yr
10 yr
11 yr
12 yr
13 yr
14 yr
15 yr
16 yr
17 yr
18 yr
19 yr
20 yr
21 yr
22 yr
23 yr
24 yr
25 yr
Your data
Class data
Your data
Class data
40
40
40
40
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Questions: 1. Look at the plotted points for your data and those of the class averages. How do they relate to the “law of averages” described in the introduction? 2. Describe the appearance of your graph line: is it straight or curved? ________ Based on your answer, why do you think radioactive decay rates are measured in half-lives and not something like decays per hour? 3. This sort of lab is known as a simulation, with each component being analogous to some aspect of the actual
radioactive decay of an isotope. For example each bead on its side is analogous to a radioactive nucleus. What are each
of the follow components analogous to:
a bead on its base: _________________________________________________________________________________
one shaking of the box: _____________________________________________________________________________
a bead flipping from side to base: _____________________________________________________________________
the sound given off as the beads flip: __________________________________________________________________
the noise level in the room decreasing over time: ________________________________________________________
4. Although the analogy is a pretty good one, it does have some aspects that are not appropriate, consider each of the
following, and explain why they are inconsistent with the analogy:
during shaking, a bead might flip side to base and then back to side: _________________________________________
a bead landing on its corner: _________________________________________________________________________
your having to shake the beads: ______________________________________________________________________
stopping the shaking: _______________________________________________________________________________
opening the box to look inside: _______________________________________________________________________
removing the basium atoms: _________________________________________________________________________
5. If you wanted to modify this simulation to demonstrate a radioactive substance more stable than sidium, what might you use? Explain. 6. Use the best fit line of the pooled class data to estimate the half-life of the sidium atoms. Do this by picking a point on the line, noting its y-value (number of un-decayed atoms), then determining how far you must move to the right along the x-axis to get a y-value half of the original one. Repeat this two more times on different parts of the line, then average your three half-life values. Then do this for the pooled shortium data. (Include units in your answers.) 7. a) Starting with a 1-mole sample (6.02 x 1023 ) of radioactive nuclei, how many nuclei will probably be left after... a) 1 half-life? b) 10 half-lives? c) 50 half-lives d) 100 half-lives? a:_______ b:_______ c:_______ d:_______
(Questions continue after the graph.)
average:
sidium shortium:
10
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8. a. In this simulation, is there any way to predict when a specific bead will “decay?” ___ b. If you could follow the fate of an individual atom in a sample of radioactive material, could you predict when it’s nucleus would decay? Why or why not? c. How could you modify the simulation to test your prediction? 9. The radioactivity levels of three different isotopes (X, Y & Z) were monitored over a 7.5 hr period and then graphed (at right). a. Which isotope was the most radioactive to begin with? ___ Which was the least? __ b. Which has the longest half-life? ___ Which has the shortest? ___ c. Which is most unstable? ___ d. Which had the biggest drop in radio-activity level during the 1st hour? ___ ...during the 5th hr? ___ e. Without using the equation, determine the half-life for Y Ans: _____ Explain how you got your answer: f. Using the log-equation, determine the half-life for X (show work) Ans: _____ g. BONUS: Approximately how many “counts” were recorded from isotope Z during the 1st hour? Ans: _____ (Hint: remember that “cpm” stands for “counts for minute”). h. Aside from uncertainty in reading the graph, why is your answer to g above not quite accurate?
150
140
130
120
110
100
90
80
70
60
50
40
30
20
10
0 0 1 2 3 4 5 6 7
time (hr)
Radio-activity
level (cpm)
X
Y
Z
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ORGANIC MODEL BUILDING Name: _________________________
1. Using clay and sticks, construct the following molecules so that the bonding electron pairs are as far apart from each
other as possible, then draw the shapes. (This should be review!)
2. Why is CF4 not square shaped?
3. What shape is CF4, and why is it this shape?
4. For each of the following molecules, construct a ball and stick model using the following code:
Once you have constructed it, draw the model as best as you can; try to convey the 3-dimensional nature of the molecule, as shown in the example at right. Then below it, write the structural formula (the “flat” representation) of that same molecule, as shown at right.
*** Now go back over the ones you’ve made and indicate if any of them have variations in how they can be put
together. By variations, we don’t just mean flipped or bent versions, we mean different bonding arrangements. These
are called “isomers”. In the little boxes, write how many isomers of each you can make. (Hint: five of them are 1’s. That
is, for five of the formulas, only one structure can be made.)
BeF2 BF3 CF4 (the wrong way!) (the right way)
CH4 CH3F
C2H6
C2H5F
C3H8
C3H7F
C4H10
C4H9F
C2H4F2
C H
C H
H H
F F
black = carbon (C)
yellow = hydrogen (H)
red = oxygen (O)
orange = fluorine (F)
green = chlorine (Cl)
C H H
F F
H
C
H
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Note Sheet for Organic naming power-point tutorial Name: _______________________
1) name: _____________________
2) name: _____________________
3) name: _____________________
4) name: _____________________
5) name: _____________________
6) name: _____________________
7) name: _____________________
8) name: _____________________
9) name: _____________________
10) name: _____________________
11) name:
____________________
21) 2,2-dichlorobutane
22) 1,2-dibromo-1-ethene
23) 4,6-difluoro-1-hexyne
24) 2-iodo-4-methylpentane
25) 3-ethylhexane
26) 1,1,3,3-tetrafluorocyclobutane
31) 3,4,4-tribromo-2-iodoheptane condensed structural formula: _______________________
32) 4-methyl-2-hexyne condensed structural formula: _______________________
33) 1-bromo-3-fluoro-3-iodocyclopentane condensed structural formula: _______________________
34) hectane condensed structural form: ________________
35) 27-fluorohectane cond str form: ________________
36) 2-bromononane molecular formula: _______________
37) 1,2,6-trichloro-3-decene mol form: _______________
12) name: _____________________
13) name: _____________________
14) name: _____________________
15) name: _____________________
16) CH3CHFCH2CH3 name: _____________________
17) CH3CH2CH=CHCH2CH2CH2CH3 name: ________________
18) CH3CH2CHCH3CH2CH2CH3 name: ___________________
19) CH3(CH2)6CF2CH2CH3 name: _____________________
20) name: _________________
27) 4-chloro-2-nonyne line formula:
28) 4,4-dimethyl-6-ethyldecane line formula:
29) 1,1,3-triiodocyclooctane line formula:
30) 2,4-dimethylcyclohexene line
formula:
38) 1,1-diiodocyclobutane mol form: _______________
39) 2,3-dimethyl hexane mol form: _______________
40) 74-chloro-34-hectyne mol form: _______________
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ISOMERS WORKSHEET Name: _________________________ The building blocks: Definition: Isomers = substances with the same chemical formula but with different arrangements of the atoms. example C4H10 and C4H10 short-cut: (leave out H's) Note: Molecules are constantly being bent, twisted and flipped as they collide with one another, but this does not change their bonding arrangements. Thus, bending, twisting and flipping of a structural formula does not create new isomers. So and and and and and are not isomers, they are all repeats of the same structure: a four-C chain with a C branching off the second C. But is a new isomer. It’s different. --------------------------------------------------------------------- Consider the following chemical formulas: In the spaces provided, draw as many different structural formulas (isomers) as you can. For 1-24, many have only 1 or 2 possible structures, and none of them has more than six (see answers below), so many of the boxes will be left empty. If only one possible structure exists, draw it and write a "1" in the space after the formula below. If more than one structure exists, draw all of the possible isomers (but no repeats), and indicate how many are possible in the space. If a compound is impossible, then don’t draw any isomers and write "X" in the space. If a compound can only exist as a free radical (a molecule containing open bonding sites), then draw just one version of the free radical, using a dot ( ) for the open bond and write "F" in the space. For compounds #25-30, more than six isomers exist. Draw just six, and then for bonus, draw all possible isomers on a separate sheet, and indicate the total number you came up with in the space. Ans (for 1-24 -- IRO +2): X, X, F, F, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 4, 4, 4, 4, 5, 5, 6 1) CH4 ___
2) CH5 ___
3) C2H6 ___
4) CH3 ___
5) CH3F ___
6) C2H7 ___
7) C3H8 ___
8) CH2F2 ___
9) C2H5 ___
C C C C H H H H
H
H H H H
H C C C
C H H H
H
H
H H H
H
H
C C C C C C C
C
C C C C
C
C C C C
C C C C
C
C C C
C
C
C
C C
C C
C
C
C
C C
C
C
C
C C
C
C N H O F Cl
L
F Br
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10) C2H5Br ___
11) CH4O ___
12) C2H6O ___
13) C2H4F2 ___
14) C2H3F3 ___
15) C2H6O2 ___
16) C3H7F ___
17) C3H9N ___
18) C3H6FBr___
19) C3H8O ___
20) C4H9Cl ___
21) C2H4 ___
22) C2H2 ___
23) C3H6 ___
24) C4H8 ___
25) C7H16 ___
26) C6H13Br___
27) C5H10 ___
28) C5H8 ___
29) C4H8O ___
30) C5H10F2 ___
Again, for these last six compounds (#25-30), way more than six isomers exist. Draw just six, and then for bonus, draw all possible isomers on a separate sheet, and indicate the total number you came up with in the space.
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More on Isomers Name: ________________
Construct models for each of the following and write down how many structural isomers there are?
1. C3H6 ___
2. C2H4 ___
3. C2H3F ___
4. C2H2FBr ___
5. C2H2 ___
6. C2FBr ___
7. C3H5Br ___
8. C2H4FBr ___
9. CHFBrI ___
10. C4H9F ___
11. C3H4FBr ___
C = black F = orange Cl = green Br = yellow I = purple H = (omit)
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Naming of Branched Alkanes… Name: _________________
Always look for the longest “straight” chain, then number the chain to give the lowest set of numbers to the branches.
1.
2.
3. CH3-CH-CH2-CH-CH-CH2-CH2-CH3
4. CH3-CH-C-CH2-CH-CH2-CH3
5.
6.
C C C C C C C
C
C
C C
C C C C C C C
C
C
C
C
C
C
CH2
CH2
CH2
CH3
CH2
CH3
C
CH2
CH2
CH3
CH2
CH3
CH2
CH3
CH2
CH3
CH2
CH3
Ans: 4,5-diethyl-3,3-dimethylheptane 4,5-diethyl-2,5-dimethyl-4-propyloctane 4,4,6-triethyl-3-methylnonane
5-ethyl-2,4-dimethylheptane 5-ethyl-3-methyl-6-propyldecane 6-ethyl-3,6-dimethyldecane
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Functional Group Group Activity! (30 pts) Name: ______________________
There are seven organic functional groups you and your teammates will focus on today: alcohols, aldehydes, ketones,
carboxylic acids, ethers, esters and amines.
Examples:
funct grp structural formula name
alcohol 2-butanol
aldehyde 4-bromopentanal
ketone 3-hexanone
carb. acid propanoic acid
ether ethyl propyl ether
ester butyl propanoate
amine butyl methyl amine
C C C C
C C C C
C C C
C C
C C C
C C C C C N
H
OH
C
O
C C C
O
C
O
OH
C C O
__ CH3CH2CH2CHO
__ CH2ICH2OH
__ CH3CH2NH2
__ CH3CH2COCH3
__ CH3CH2OCH2CH2CH3
__ CH3CH2COOH
__ CH3CH2CH2COOCH2CH3
Try the following matching problems first. Call the instructor over each
time you finish a problem so he may score you on it. He may pick any
group member’s page, so make sure everyone in the group has the
answers correct.... in their own handwriting! Each question is worth 3 pts.
a) alcohol
b) aldehyde
c) ketone
d) carb. acid
e) ether
f) ester
g) amine
O O
OH
NH2
O
OH
O
1 2
READ THIS: For 3-9, fill out the row with the appropriate representations and build the model (leave off all H’s, but
include the bonds to the H’s). NOTE: When numbering, always give the functional groups the lowest
number possible on the carbon chain. So is 6-fluoro-3-hexanol (not 1-fluoro-4-hexanol).
structural formula name line formula condensed structural formula func. grp.
C C C C C C
OH F
3
4
5
6
7
8
methyl propyl amine
2-methylheptanoic acid
C C C C
O F
O
CH3CF2CHF(CH2)4CHO
OH
Br
Br
C = black N = blue O = red F = orange Br = yellow
19
C C C C C
O
C C O
Br
O O
F
CH3(CH2)3COOCH2CH3
Polymer Identification Lab Name: _________________ partner: ____ ____________
Have you ever noticed those recycling numbers on plastic containers? Before there was
single-stream recycling, those numbers played a much more significant role, since consumers
who chose to recycle would have to sort not only glass from metal from paper from plastic,
but also sort the different types of plastics. As you have learned already, plastics are made of
polymers, which are carbon-based compounds with very long molecular chains. Each polymer is named after the
monomer links which are strung together to form those long chains. For example number 6 is named polystyrene since
it is made by stringing together tens of thousands (or more) of repeating styrene molecules. The names of the six
recyclable polymers are listed in the table at right. Note that these are
not the only plastics that are commercially produced (plastics like nylon,
Teflon (tetrafluoroethylene), and polyurethane are not on the list);
these six, however, are the ones that are most commonly used for pack-
aging and are most economical to recycle. [Actually, #6, polystyrene is
currently not very economical to recycle, which is why consumers are
supposed to separate it out from the other plastics they put in their
recycling. This lab activity is intended to point out the inherent differences among these six common polymers, to
identify them by these differences, and to illustrate why not all plastics can be used or recycled in the same manner.
Materials: index card, copper wire, cup of water, beaker of boiling water on hot plate, burner, beaker of acetone (keep
covered, away from flames), cup of 45% 2-propanol (rubbing alcohol, colored green), tongs, forceps, stirring rod, scissors
Procedure:
I: POLYMER ID: Take the index card up to the polymer samples and pick out one sample of each A, B, C, D, E & F, and
place it next to its corresponding letter on the card. Just to help you from getting these mixed up, take a photo of these
six plastics on the card using either your iPad or phone. These samples A – F correspond with plastics 1 – 6, but they are
in a scrambled order. Your task is to determine which letter corresponds with which number.
1. DENSITY TEST #1: Place all six samples in the cup of water. Poke them with the stirring rod if necessary to dislodge
any adhering bubbles. Record your observations below, and use the density table below to help you begin to limit your
choices. Can you identify any of them yet? [Each polymer has its own unique density range, and whether a polymer
floats or sinks in a liquid should help you identify it. This process is also
used in plastic recycling plants to separate out the plastics!]
Observations:
PROCEED WITH TESTS 2-4 WITH ONLY THOSE SAMPLES THAT SANK IN WATER 2. COPPER WIRE TEST: Hold the end of the copper wire in the hottest part of a hot flame until it glows red hot. Remove
the wire from the flame, and while it is still hot carefully push it through one of the sinking samples, then pull it back out.
Place the wire (not the plastic sample) back in the flame and record your observations below. Repeat this test with the
other plastic samples that sank in water in test #1. [The halogens (F, Cl, Br and I) will often steal electrons from copper
atoms to produce copper(II) ions. When these ions have their remaining electrons excited by heat energy, they give off
a unique colored light. Use the polymer names above to help narrow down your choices. Can you identify any of them
yet? You should be able to identify one, and once you have, don’t bother running any more tests on it.]
Observations:
#1 = PET (or PETE) = polyethylene terephthalate
#2 = HDPE = high-density polyethylene
#3 = PVC (or V) = polyvinylchloride
#4 = LDPE = low-density polyethylene
#5 = PP = polypropylene
#6 = PS = polystyrene
Density ranges (in g/mL) for plastics #1-#6
#1 PET 1.38-1.39 #4 LDPE 0.92-0.94
#2 HDPE 0.95-0.97 #5 PP 0.90-0.91
#3 PVC 1.16 – 1.35 #6 PS 1.05-1.07
20
3. ACETONE TEST: NOTE: acetone is safe to touch, but it will act to dissolve finger nail polish, so if you have manicured
nails you care about, avoid getting acetone on them! Go to the separate table for the acetone – kept covered and away
from the flames, because acetone is quite flammable. Use the tongs to hold one of the sinking polymer samples in the
acetone for five seconds. Then remove it from the acetone and press it firmly between your fingers. Record your
observations below. Repeat this test with the remaining samples that sank. [The polymer chains made from repeating
styrene units will loosen up in acetone (this is known as “swelling”), allowing the polymer’s surface to become soft and
impressionable.
Observations:
4. HEAT TEST: Using forceps, hold one of the sinking samples in the boiling water for a few seconds. Record your
observations below, and repeat with the other samples that sank. [Heat can also cause polymer chains to loosen up and
soften. (This is how many plastics are molded into their desired shapes.) Different polymers have different softening
points. PVC’s, for instance, is rather high, whereas PET’s is relatively low.]
Observations:
PROCEED WITH TESTS 5 & 6 WITH ONLY THOSE SAMPLES THAT FLOATED IN WATER 5. DENSITY TEST #2: Place the samples that floated in water in the cup of 45% 2-propanol (colored green) and if
necessary, poke with the stirring rod to dislodge any adhering bubbles. Record your observations below. [Refer back to
the density table. As before, this should help you narrow down your choices.]
Observations:
6. COMBUSTION TEST: (Caution: this test may produce hot dripping plastic – perform it over a cleared-off portion of the
lab bench.) Use a pair of scissors to obtain a small strip of the sample about this big: Using forceps, hold the
very tip of the strip in the burner flame until it begins to burn, then remove it from the flame and observe it as it burns.
When the reaction is over, quench the molten sample in the beaker of water. Scrape off the residual plastic and repeat
this test with the other samples that floated in water (from step 1). [Polyethylene burns slowly, allowing enough oxygen
to react to give a hot, blue flame. Polypropylene, on the other hand, burns quickly, causing incomplete combustion and
a somewhat cooler, yellow (and sometimes sooty) flame. Note: the difference is not always as pronounced as one might
hope. Thus it may be difficult to distinguish between these two plastics. Do your best!]
Observations:
II More Unknowns: If time permits, obtain three more samples, of your own choosing from the other unknowns labeled
G through X. They also match up with polymers 1-6 above, but since you are picking three random unknowns out of
eighteen, you could easily end up with repeats! See if you can determine their identities using the fewest tests possible.
Record observations below.
Observations:
21
Polymer ID Lab Turn this sheet in at the end of the period: Names: __________________ ______________
Identifications: A = ___ B = ___ C = ___ D = ___ E = ___ F = ___ More: ___ = ___ ___ = ___ ___ = ___
Questions:
1. From what you observed, approximate the density for the 45% 2-propanol (green) solution? _________
Explain how you approximated this.
2. Why was it important to dislodge any adhering bubbles in the two density tests?
If you hadn’t done this, it might have caused you to…
a)… mistake an LDPE sample for a HDPE b) … mistake an HDPE sample for an LDPE (circle one)
Explain.
3. Why would it not be wise to make a canoe paddle out of solid PVC?
What would be a better polymer from which to make a canoe paddle? ______
If all you had was PVC to make your canoe paddle, what might you do?
4. You wish to make a plastic handle for a frying pan; which type of plastic should you not use? _____
Explain.
5. Sometimes plastics are burned rather than recycled. Which would make a relatively good fuel? ____
Give at least two reasons for your choice.
6. You decide to jazz up your bathroom cabinet by transferring your fingernail polish remover into a more stylish pink
plastic bottle. The next day, reaching for the bottle, all you find is a messy pink blob of goo. What was the bottle
probably made of? _____ What was the active ingredient in the nail polish remover? ________________
7. Three different samples ( X, Y & Z) are placed in salt water: Y sinks. When pure water is mixed in, X sinks. After even
more water is mixed in, Z eventually sinks. Identify (PP? PET?) the three samples: X = _____ Y = _____ Z = _____
8. Below is a simple flow chart that could be used to distinguish
between 1) a cardinal, 2) a blue jay, 3) a canary, 4) an ostrich and
5) a bald eagle (for someone new to bird-watching). In the box at
right, construct a flow chart for identifying the six polymers 1, 2,
3, 4, 5 & 6.
22
Does it have a crest?
What color is it? Does it sing?
Does it fly?
yes
yes
yes
no
no
no
red blue
It’s a cardinal
It’s a blue jay
It’s a canary
It’s an eagle
Write the numbers 1 – 6 in the spaces above
It’s an ostrich
A Tale of Two Cross-Linked Polymers! Name: _____________________
“It was the best of slimes… it was the worst of slimes…”
When most people think of polymers, they think of plastics, but polymers can be powders and sometimes they can be
dissolved in solvents like water. Polyvinyl acetate, used in glues, and polyvinyl alcohol, used to increase viscosity in
pharmaceuticals, are two polymers that are both quite water soluble (see their molecular structures below). An
interesting thing happens when borate ions (BO33-) are added to solutions of these polymers: the borate ions act to
crosslink the polymer chains – turning what would be a bunch of separate “ropes” into something more like a
“hammock.” Needless to say, this greatly changes the viscosity of the polymer solution.
Procedure A: (to make cross-linked polyvinyl acetate)
1) Pour 15 mL of water into the plastic vial and add 1 small spoon of sodium borate (sold in stores as Borax laundry
additive), screw on the cap and shake for 15 seconds. Let this sit undisturbed to allow the undissolved sodium borate to
settle to the bottom of the vial.
2) While it is settling, carefully pour 20 mL of water into the small cup (up to the W line), then add in 20 mL of glue (to
the G line). If you want, go up to the central lab bench and add 3-4 drops (NO MORE) of food coloring (your choice of
colors). Stir with a coffee stirrer for 30-45 seconds until it is uniform consistency throughout. Then transfer the
glue/water mix into a plastic ziplok bag.
3) Carefully decant the 15 mL of sodium borate solution from the vial into the bag, being sure to leave any undissolved
sodium borate behind.
4) Get most of the air out of the bag, zip it closed, and then start kneading the bag. What do you notice happening to
the viscosity of the polymer solution as the borate ions cross-link the polymer chains together?
polymerizes into polyvinyl acetate, the polymer in glue
polymerizes into polyvinyl alcohol
vinyl acetate
vinyl alcohol
23
5) Keep kneading the bag and rolling it between your palms to the point where the inside of the bag is pretty much
“clean.” Then open the bag and take out your cross-linked polyvinyl acetate.
Procedure B: (to make cross-linked polyvinyl alcohol)
1) Pour 15 mL of water into the plastic vial and add 1 small spoon of sodium borate (sold in stores as Borax laundry
additive), screw on the cap and shake for 15 seconds. Let this sit undisturbed to allow the undissolved sodium borate to
settle to the bottom of the vial.
2) While it is settling, carefully pour 40 mL of PVA solution into the plastic cup (up to the G line). If you want, go up to
the central lab bench and add 3-4 drops (NO MORE) of food coloring (your choice of colors). Stir with a coffee stirrer for
30-45 seconds until it is uniform consistency throughout. Then transfer the PVA solution into a plastic ziplok bag.
3) Carefully decant the 15 mL of sodium borate solution from the vial into the bag, being sure to leave any undissolved
sodium borate behind.
4) Get most of the air out of the bag, zip it closed, and then start kneading the bag. What do you notice happening to
the viscosity of the polymer solution as the borate ions cross-link the polymer chains together?
5) Keep kneading the bag and rolling it between your palms to the point where the inside of the bag is pretty much
“clean.” Then open the bag and take out your cross-linked polyvinyl alcohol.
CLEAN UP – Get the cup completely clean and leave it upside down on the lab bench.
Now what can you do with the slime?
A) Resiliency Test: Roll it into a ball. Can it bounce? Caution: do not throw it too hard!
B) Stretchability Test: See what happens when you try to stretch it very slowly compared to very quickly. Why do you
think this happens?
C) Viscosity Test: Place your slime sample in a funnel (plastic bottle top) and time how long it takes to flow all the way to
the table. Is the flow rate constant? Is the time reproducible?
D) Inflatability Test: Form the slime sample into a ball around the end of the straw and inflate it by gently, SLOWLY
blowing into the other end. You will need to pinch the slime together around the end of the straw to prevent the air
from leaking out the sides and making disgusting flatulent noises.
When you are done, return the slime to the bag and take it with you. At home make sure to keep it away from carpets
and upholstery… and hungry pets. Also know that since no antibacterial agents were added, your slime will start to go
moldy in about a week or two, at which point you should throw it away.
Concentrated polyvinyl
acetate chains in glue…
… are diluted with water to
spread them out a bit… … and the borate ions cross-link
the chains together into a loose
random web-like polymer (SLIME!)
… then
borate ions
are added…
24
Molarity WS Name: _________________ 1. What is the molarity of a solution containing…
a) 1.75 mol KBr in 3.4 L of soln _____ b) 0.62 mol Br2 in 925 mL of soln _____ c) 0.35 mol NaF in 42.4 mL of soln _____ 2. What is the molarity of a solution containing…
a) 213 g of KBr in 3.4 L of soln _____ b) 58.2 g of Br2 in 925 mL of soln _____ c) 3.45 g of NaF in 42.4 mL of soln _____ 3. How many moles of solute are needed to make…
a) 2.30 L of 0.457 M NaCl soln _______ b) 0.785 L of 1.25 M KNO3 soln ______ c) 145 mL of 0.525 M C6H12O6 soln? ______ 4. What mass of ethanol is needed to make 75.0 mL of 2.45 M solution? _________ 5. When 19.0 mL of 0.350 M NaNO3 solution are evaporated in a 9.75 g petri dish, what will be the total mass of the petri dish and recovered NaNO3 crystals? ________ 6. What volume of 0.600 M Na2SO4 soln could be made with 2.87 moles of Na2SO4? ______
7. How many milliliters of 2.50 M CuBr2.4 H2O can be made from 135 g of CuBr2
.4 H2O? _______
8. How many CO2 molecules are dissolved in a 525 mL bottle of Pepsi – with a CO2 conc of 0.15 M? _______
9. 7.82 x 1018 molecules of propanol are dissolved 267 L of solution. What is the molarity? ________ 10. What mass of 2,3-difluoro-2-methylpentane is needed to make up 17.5 L of 0.500 M soln? ________ 11. What mass of magnesium would be needed to react with 25.0 mL of 3.00 M HCl soln? ________ Mg + 2 HCl H2 + MgCl2 12. 17.5 mL of 1.50 M AgNO3 are mixed with a solution containing excess Na3PO4. A silver phosphate forms. When this precipitate is filtered and dried, how much will it weigh? __________ Write a balanced equation first. 13. a) One grain of sugar (glucose = C6H12O6 ) weighing 0.024 mg is dissolved in a 25.0 m x 2.0 m x 5.0 m swimming pool filled with water. What is the molarity of this solution? _________ b) How many molecules of glucose would there be in 1 drop (0.050 mL) of that sweetened pool water? __________
5.3x10-13
0.0487 0.0761 0.394 0.51 0.53 0.67 0.911 0.981 1.05 1.94 3.66 4.78 8.3 8.45 10.32 183 725 1070 1.6 x 10
7
4.7 x 1022
(M)x8 (mol)x3 (g)x5 (cules)x2 mL L
25
Mixtures and Dilutions: 14. What is the resulting concentration of the mixture of…
a) 3.15 L of 3.00 M NaBr & 1.23 L of 5.00 M NaBr? _________ b) 255 mL of 1.00 M HCl & 175 mL of 2.50 M HCl. ________ c) 25.0 mL of 4.00 M LiNO3 and 45.3 mL of water? ______ d) 34.5 mL of 3.45 M KBr, 17.8 mL of 2.95 M KBr & 24.8 mL of 1.64M KBr? ________
15. 45.7 mL of 0.750 M HNO3 soln is diluted with water to make 500 mL of solution. What is the new conc? _________ 16. What volume of water must be added to 56.9 mL of 3.50 M NaF solution to dilute it down to 1.85 M? ________ 17. What volume of 2.50 M CsBr soln must be mixed with water to make up 1500 mL of 0.175 M solution? ________ 18. Explain, step-by-step with diagrams and words how you would go about making up 250 mL of 1.45 M NaNO3 solution starting with solid NaNO3 and water. 19. Explain, step-by-step with diagrams and words how you would go about making up 250 mL of 1.45 M NaNO3 solution starting with some 5.00 M NaNO3 solution and water.
0.0686 1.42 1.61 2.75 3.56 30.8 50.7 72.5 88.8 105 (M)x5 (mL)x3 g
26
TIE-DYE T-SHIRT LAB Name: _______________________ Per: ___ PROCEDURE: Twelve steps to a perfect tie-dye! Day 1: 1. Pick out the size shirt you want. Use a permanent marker to write your name on the tag. 2. Soak your T-shirt in the large basin of sodium carbonate solution for at least 15-20 minutes. This solution removes “sizing” or fabric fillers and therefore helps open up the bonding sites on the cotton molecules (cellulose polymer chains) to give the dye molecules a place to bond covalently. 3. While the T-shirt is soaking, practice designs and color mixings on damp paper towels. Wet the paper towels with tap water then wring them out completely, carefully open them up and try different folding and dye application patterns. There will only be five colors available: blue, yellow, red, viridian (aquamarine) and fuchsia (dark pink). If you want a green or orange, etc, you will need to mix them yourself. To do this, squeeze 6 drops of yellow and 4 drops of fuchsia (for example) into a small test tube. Then just pour out a few drops of this mixture onto a spread out moistened paper towel. If this isn’t quite the orange you wanted, rinse out the test tube and try 7 drops of yellow and 3 drops of fuchsia. It’s best to try to keep the total drops at 10. When you find a mixture you like, right down the proportions. 4. Take the T-shirts out of the mordant solution and run them through the wringer. Watch your fingers. There’s nothing worse than a painful case of “wringer finger!” Place the wrung-out T-shirts on a coat hanger and hang them up to dry overnight in the lab room. Day 2: 5. Working with a friend, with your desks scooted together, fold and wrap your T-shirt in any of a number of ways discussed (spirals are easy and always turn out great). Use rubber bands to hold them together. 6. Take the wrapped shirt into the lab, place a single newspaper sheet folded in quarters on a plastic tray and begin dyeing. First, though, figure out how much dye you will need and what colors you want to use. You and your partner will have four squirt bottles to use between the two of you.
shirt size Short Sleeve Long Sleeve
Volume (mL) for 90% coverage
Volume (mL) for 100% coverage
Volume (mL) for 90% coverage
Volume (mL) for 100% coverage
XS 260 290 360 400
S 280 310 390 430
M 300 330 420 470
L 320 370 470 520
XL 380 420 530 590
XXL 420 480 610 680
That means an XXL short sleeve shirt will need 480 mL of total dye. So if you want the shirt to be half red and half orange (that is 7 parts yellow and 3 parts fuchsia), you will put about 240 mL ( of 480)
of red in one squirt bottle, and 240 x 70% = 168 mL of yellow and 240 x 30% = 72 mL of fuchsia in the second squirt bottle. (You can eyeball this or use graduated cylinders.)
27
7. VERY IMPORTANT: Make as little mess as possible, and clean up after yourself as you go. When you go up to fill up the squirt bottles, leave the tops at your lab station hanging in the cut-off soda bottles. And keep the tips in the cut-off soda bottles as you screw-on and/or screw-off the tops. Get the dyes you need from the dye vats at the center lab table, then go back to your lab area to put the lids back on. Then gently squeeze the dye out onto the shirt making slow sweeping movements to allow the dye to spread evenly. Also, be aware that mixing will occur where the dyes come in contact with each other. Using complimentary colors (purple & yellow, blue & orange, red & green) near each other usually produces a brownish black color. These dyes are known as “fiber-active” dyes; that means they actually form covalent bonds with the cotton molecules, and are therefore essentially impossible to wash out. (By the way, bleach does not really wash out the molecules, it just breaks them up so they no longer show the colors they normally do. Bleach also breaks up the cotton fibers and will eventually lead to holes in the shirt!) 8. Take a fresh piece of newspaper (just one sheet and fold it down so it is the same size as your shirt. Place this on the foam board for your class, then transfer the T-shirt onto this folded up newspaper. It will stay there for at least 24 hours. This gives the dye time to bond to the fabric, and as the water evaporates, it concentrates the dye to give richer colors. 9. When both you and your partner are done, thoroughly clean up your lab station, rinse out the bottles and tops, throw away the old newspaper sheet, use a cheap paper towel to wipe up your tray (and the lab area) and place a fresh single sheet of newspaper in the tray for the next person. Then wash your hands well. Day 3: 10. The next day, at the end of class, place your T-shirt in a grocery bag and take it home. (Hint: Be careful not to let it stain things such as upholstered car seats as one careless student did a few years ago!) When you’re ready, remove the rubber bands, open the shirt up (say “Ooooo” or “Ahhhhh”) and place it in a large bucket of water. Rinse it a few times, wring it out, then continue to rinse it with fresh, clean water until the rinse water comes out dilute enough so that you can see your hand through about 5-6 cm (2 in) of the water. You may want to wear gloves while doing this. This rinse water is safe to dump on the grass. 11. Wring out the T-shirt one final time, then wash it in the washing machine by itself (small load setting to conserve water) in hot water using dish detergent (about 1 teaspoon!) such as Dawn or Joy (not laundry detergent). Dry it (by machine on hot setting). Note: Some dryers have trouble drying just one item, so if you have a bunch of rags or clothes that you don’t care about, throw them in there too. The first few times you wash it, you may want to wash it by itself, but after that, the shirt can be washed with other darks in cold water. 12. To receive credit for this lab, wear your T-shirts to school on ____________ . Bring $12 for
short sleeve or $15 for long sleeve, (checks made out to KHS). Or if you’re not keeping it,
turn it in immediately after the class picture.
28
Tie-dye Questions: 1. On the back of the last page, describe precisely using words and diagrams how you wrapped
your shirt and then draw two COLORED pictures below the description: one that depicts how you
thought the shirt would turn out and the other that depicts how it actually turned out.
2. Cotton is made of a natural polymer called cellulose, which is also the main fiber in wood and
paper (a polymer is a carbon-based substance with very long chain molecules made out of repeating
units, called monomers). The structural (line) formula for cellulose is:
Here’s what these structures represent. The structures are a short-cut way of writing the structure of
organic molecules. At the end of each line segment, if no element symbol is shown, there is a carbon
(C) atom. Carbon can bond to four other elements so any missing bonds go to hydrogens (H).
a. Cotton is very absorbent when it comes to water. Based on the structure above, and based on
what you know about water and intermolecular forces, why is this so?
b. Circle one of the repeating units above, then, knowing what you know about line diagrams,
determine its molecular formula (hint: it starts off C6...) Answer: ________
c. When cellulose is made from its monomer, one water molecule is taken out for each monomer
unit, so add two H’s and one O to your formula above to determine the molecular formula of the
monomer from which it was made (hint: it should look familiar) Answer: ________
d. Based on its formula, what is the name of the monomer from which cotton is made? ________ e. Where exactly does cotton come from (plant, animal, petroleum product?) _________________ f. Where did the energy come from to make those monomer units? ________________________ g. What is this process (in f) called? _____________________________
EQUALS C
C
C
C
C
C
C
C
C
O
O
OH
OH
HO
OH
OH
HO
O
O
C
C
C
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
29
3. a. The soaking solution used in this lab was sodium carbonate, also known as soda ash. What is
its molecular formula? __________
b. Your shirt soaked up about 15.0 g of sodium carbonate. How many moles is this? _________ ___________________________________________________ 4. To get the dyes to dissolve, they must be mixed with a white granular
substance called urea (which you may have heard of!): CON2H4.
a. Draw the structural formula for urea: (Hint: the molecule is symmetrical
and neither the C nor the O is bonded to any H’s!)
b. Looking at the structural formula you drew for part a, what tells you that the urea would
dissolve quite readily in water? (Hint: what type of attractive forces would exist between urea and
water?) ___________________________________________________________
c. Your shirt soaked up about 2.4 x 1022 molecules of urea. How much did this weigh??
Ans: ______
5. What is a mordant? ___________________________________________________________
6. What is a “fiber-active” dye? ____________________________________________________
7. How does bleach clean stains? _________________________________________________
8. Three of the fiber active dyes you used are shown below. They all have one part of the molecule
that allows them to bond to the fibers and a separate part (called the chromophore) that produces
their unique color. For one of the molecules these two sections have been indicated as “A” and “B”.
Based on comparisons with the other molecules shown. Which section (A or B)
is the fiber-bonding part? ___ Which is the “chromophore” part? ___
9. Explain your reasoning.
30
10. Carol wants to dye a medium sized shirt but leave a little white. She wants it to be half fuchsia
and half green (made from 6 parts blue and 4 parts yellow). How many milliliters of each dye does
she need to use?
fuchsia: _____ blue: _____ yellow: ______
11. Tony wants to dye a large T-shirt (with long sleeves). He wants no white, and the shirt to be 1/3
blue, 1/3 red and 1/3 burgundy (made from 3 parts viridian and 7 parts fuchsia). How many milliliters
of each dye does he need to use?
blue: _____ red: _____ viridian: ______ fuchsia: _____
12. For each of the following folding and dying techniques, draw and color in the pattern you would
expect it to produce:
31
Acid Base WS Background information
H+ and OH-: First, it is important to understand that water molecules have a very slight tendency to spontaneously break apart into hydrogen ions (H+) and hydroxide ions (OH-): H2O(l) H+
(aq) + OH-(aq) These two ions dissolve in the water
that surrounds them, but they don’t last long in solution – they quickly revert back into H2O molecules whenever two of them encounter one another: H+
(aq) + OH-(aq) H2O(l) . These two reactions are usually written as just one with a double
arrow: H2O(l) H+
(aq) + OH-(aq) This reaction is said to be at equilibrium. This does not mean that there are equal
amounts of H2O molecules and H+ & OH- ions. It simply means that the forward reaction rate and the reverse reaction rate are equal, and so the concentrations of the reactants and products are remaining constant. In fact, at any point in time, only about one out of every 550 million H2O molecules is split into H+ and OH- ions. This makes the H+ concentration (written [H+]) around 1.0 x 10-7 M, and the OH- concentration (written [OH-]) also around 1.0 x 10-7 M.
Acidic & Basic: Having dissolved H+ ions gives a solution a certain set of properties – tasting sour, for example, and reacting with metals to make hydrogen gas – and these properties make that solution “acidic.” The higher the [H+], the more acidic the solution is. Having dissolved OH- ions gives a solution a different set of properties – tasting bitter, for example, and feeling slippery on the skin – and these properties make that solution “basic.” The higher the [OH-], the more basic the solution is.
pH and pOH: Sometimes it is convenient to talk about the [H+] logarithmically – in terms of its power of ten. For a concentration of 1.0 x 10-7 M, that power would be -7. [Conventionally chemists change the sign and just say “7”]. This is referred to as the “power of the H+ ion,” or simply “pH.” So a solution with a [H+] of 1.0 x 10-7 M is said to have a pH of 7. There is also a pOH which refers to the power of a solution’s [OH-]. Since ordinary water has a [OH-] of 1.0 x 10-7 M, it has a pOH of 7 as well. And since ordinary water has equal concentrations of H+ and OH- ions, it is equally acidic and basic, and is referred to as “neutral.” Any solution with a pH of 7 is by definition neutral.
Acids and Bases: If a substance like HCl is dissolved in water, it dissociates into H+ ions and Cl- ions, and it will make the [H+] go up, and that in turn makes the [OH-] go down. Such substances are known as “acids.” Likewise, if a substance like NaOH is dissolved in water, it will dissociate into Na+ ions and OH- ions and this will make the [OH-] go up, which in turn makes the [H+] go down. Such substances are known as “bases.” Here’s the neatest thing about this equilibrium, no matter which of these two ions is present at a greater concentration, the product of these two concentrations must always be 1.0 x 10-14! In other words: [H+] x [OH-] = 1.0 x 10-14. So if we add enough HCl to water to make the [H+] go up to 1.0 x 10-4 M, the [OH-] must drop to 1.0 x 10-10 M. [That you should be able to do in your head!] And if we add enough NaOH to water to make the [OH-] go up to 2.7 x 10-2 M, then that means the [H+] must drop to 3.7 x 10-13 M. [That one you would probably need a calculator for!] Since the product of the [H+] and [OH-] is always 1.0 x 10-14, it is always easy to determine concentration of one of these ions if you know the other: You simply take 1.0 x 10-14 and divide it by whichever one you know, and it gives you the other one. So above, when we knew that the [OH-] was 2.7 x 10-2 M,
we simply calculate the [H+] to be 1.0 x 10-14
/2.7 x 10-2 = 3.7 x 10-13 M.
pH scale: The HCl solution described above has a relatively high [H+] of 1.0 x 10-4 M and this would give it a pH of 4 (and a pOH of 10). Since this solution has more H+ ions than OH- ions it behaves more as an acid than it does as a base, so it is considered acidic. Any solution with a pH less than 7 is by definition acidic. Likewise the NaOH solution described above has a very low [H+] of 3.7 x 10-13 M and this would give it a pH of 12.43* (and a pOH of 1.57). Since this solution has many more OH- ions than H+ ions it behaves more as a base than it does as an acid, so it is considered basic. Any solution with a pH greater than 7 is by definition basic.
*Calculating pH: To calculate the pH for a solution with a [H+] of 1.0 x 10-4 M is easy: you just look at the power of ten and then change the sign: pH = 4. But when you do this, what you are actually doing in your head is taking the log of the [H+]! For numbers that do not start with 1.0 x… you really need to use a calculator: so when the [H+] was 3.7 x 10-13 M, take the log of this number (-12.43) and change the sign: pH = 12.43. It’s that simple. The equation is: pH = -log[H+]. (Likewise, pOH = -log[OH-], but we don’t use pOH all that much). And what if you are given the pH and asked to find the [H+]? If it’s a whole number, it’s easy: If the pH is 9.00, the [H+] is simply 1.0 x 10-9 M. But what if the pH is 9.25? Now you need a calculator: simply find the antilog (which is the same as 10x) of -9.25. The antilog of -9.25 gives 5.6 x 10-10 M for the [H+]. Notice one more thing: just as the [H+] and [OH-] must always multiply out to 1.0 x 10-14, since the pH and pOH are their logarithms, the pH and the pOH must always add up to 14.00. pH + pOH = 14.00 So if you know one of these two values, it is very easy to find the other. If for example, the pH is 9.25, the pOH must be 14.00 – 9.25 = 4.75.
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Strong and weak acids: The extent to which an acid dissociates into ions determines how strong the acid is. There exist only six truly strong acids: HCl, HBr, HI, HNO3, HClO4, H2SO4. These acids all dissociate 100%. That means that whatever the acid concentration is, that will be the H+ concentration as well. In other words, in a 0.25 M HBr solution, the HBr will completely dissociate into H+ ions and Br- ions ( HBr H+
(aq) + Br-(aq)), and this means that the [H+] will be 0.25 M – how
easy is that! (The [Br-] will also be 0.25 M, but we really don’t care much about that since it has nothing to do with the solution’s acid or base properties.) All other acids (like HF, HNO2, HC2H3O2 …) are all considered weak acids and they generally only dissociate a little in solution: like H2O, they reach equilibrium. For example: HF H+
(aq) + F-(aq). Thus a
0.25 M HF solution might be only 1.0% dissociated (in other words, at any point in time, 99% of the HF molecules remain as HF molecules, and only 1% are broken up into H+ and F- ions, as shown below). This means that a 0.25 M HF solution will have an [H+] of only 0.0025M.
Strong acids like HBr dissociate 100% in solution Weak acids like HF dissociate only a little in solution
Acid - Base reactions: Of all the reactions that acids and bases can be involved in, perhaps the most impressive is the neutralization reaction. Imagine 100 mL of 10.0 M HCl. Splash it in your eyes, and you will have permanent eye damage; drink it and you are sure to die! The same can be said of 100 mL of 10.0 M NaOH solutions. Bases are every bit as caustic and dangerous as acids. BUT… pour these two solutions together and miraculously, you end up with salt water, which would neither damage your eyes nor poison you. That is because the H+ & OH- ions that make the original solutions so dangerous combine to form good-old H2O! The overall reaction is: HCl(aq) + NaOH(aq) NaCl(aq) + H2O(l) and the net ionic equation is: H+
(aq) + OH-(aq) H2O(l) . (Since the Na+ and Cl- ions start off dissolved in solution and end up
still dissolved in solution, they are spectators and therefore don’t show up in the net ionic equation.)
This neutralization reaction only leaves a truly neutral solution (pH = 7) when the two solutions exactly use each other up, and this only occurs when there are precisely the same number of moles of the acid as there are of the base. In the example above, using 100 mL of 10.0 M HCl 1nd 100 mL of 10.0 M NaOH, since the volumes were the same and the concentrations were the same, then certainly the number of moles must be the same. If we were trying to neutralize the 100 mL of 10.0 M HCl using an NaOH solution that was only 5.00 M, we could still do it, but it would clearly take twice as much (200 mL). This is because (molar concentration) x (volume) = # of moles. If the moles of acid and base must be equal, then this means: [acid] x Vacid = [base] x Vbase.
Sample neutralization problems:
1. What volume of 0.350 M NaOH would be needed to neutralize 24.5 mL of 0.125 M HCl?
[acid] x Vacid = [base] x Vbase (0.125 M) x 24.5 mL = (0.350 M) x Vbase Vbase = 8.75 mL. (easy!)
2. It takes 21.76 mL of 0.140 M NaOH to neutralize 26.19 mL of HCl solution. What is the HCl concentration?
[acid] x Vacid = [base] x Vbase [HCl] x 26.19 mL = (0.140 M) x 21.76 mL [HCl] = 0.116 M. (also easy!)
Important: some acids have more than one H+ per molecule that dissociate into solution. H2SO4 for example has two. (Likewise for some bases: Ba(OH)2 has two OH- ions.) When you encounter such a compound, just appreciate that it acts like a doubly strong acid (or base). So 0.300 M H2SO4 has an [H+] of 0.600 M.
3. It takes 21.76 mL of 0.140 M Ba(OH)2 to neutralize 26.19 mL of HCl solution. What is the HCl concentration?
[acid] x Vacid = [base] x Vbase [HCl] x 26.19 mL = (0.280 M) x 21.76 mL [HCl] = 0.232 M. (still pretty easy!)
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Acid / Base WS Name: __________________
1. Fill out the two tables below (the first row is done for you). The left hand side you should be able to do in your head.
The right hand one will require a calculator!
[H+](M) [OH-](M) pH pOH A/B/N
1.0 x 10-5
1.0 x 10-6
3.00
12.00
N
1.0 x 10-4
Solve each of the following problems. Also, for review, name each of the acids and bases.
2. What is the [H+] and the pH of a 0.0100 M HBr solution? _________ _________ Name: ______________________
3. What is the [H+] and the pH of a 0.0375 M KOH solution? _________ _________ Name: ______________________
4. What is the [H+] and the pH of a 0.0218 M H2SO4 solution? _________ _________ Name: ______________________
5. What is the [H+] and the pH of a 0.00423 M V(OH)3 solution?_________ _________ Name: _____________________
6. What conc. of HNO3 is needed to make up a solution with a pH of 3.59? _________ Name: ______________________
7. What conc. of LIOH is needed to make up a solution with a pH of 12.53? _________ Name: _____________________
8. What conc. of H2SO4 is needed to make up a solution with a pH of 2.74? _________ Name: ______________________
9. What conc. of Ba(OH)2 is needed to make up a solution with a pH of 11.29? _________ Name: __________________
10. A 0.0250 M HBrO3 solution is 3.25% dissociated. [H+] = _________ pH = _________ Name: ____________________
11. A 0.00250 M HClO solution is 0.715% dissociated. [H+] = _________ pH = _________ Name: ___________________
12. A 0.00450 M HNO2 solution has a pH of 4.13. What is its % dissociation? _________ Name: ___________________
[H+](M) [OH-](M) pH pOH A/B/N
7.2 x 10-3
1.8 x 10-4
6.29
2.09
13.58
5.8 x 10-5
Ans: 2.6 x 10-14
2.7 x 10-13
1.0 x 10-12
1.2 x 10-12
2.4 x 10-12
1.0 x 10-11
5.6 x 10-11
1.0 x 10-10
1.7 x 10-10
1.0 x 10-8
1.9 x 10-8
1.0 x 10-7
1.0 x 10-7
5.1 x 10-7
1.8 x 10-5
2.6 x 10-4
8.13 x 10-4
9.1 x 10-4
9.7 x 10-4
1.0 x 10-3
8.1 x 10-3
0.010
0.0100 0.034
0.0436
0.38
0.42 1.36 1.6 2.00
2.00 3.09 3.74 4.00 4.24 4.75 6.00 7.00 7.00 7.71 8.00 9.76 10.00 10.26 11.00 11.91 12.57 units: M(10) % nitrous nitric hypochlorous
bromic hydrobromic sulfuric sulfuric lithium hydroxide vanadium(III) hydroxide barium hydroxide potassium hydroxide
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13. What would be the pH of a solution made by dissolving 1.35 g of NaOH in 5.85 L of solution? _________
14. How many milligrams of HCl would need to be dissolved in 475 mL of solution to have a pH of 2.35? _______
15. What volume of pH 3.58 HNO3 solution can be made from 0.0250 moles of HNO3? _______
16. What is the pH of a solution made by mixing 17.5 mL of 0.0350 M HBr with 189.4 mL of water? _________
17. What is the pH of 10.0 mL of 0.0375 M HCl solution? _______ If it were diluted to 100.0 mL, what would its pH
be? _______ If it were diluted to 1000.0 mL, what would its pH be? _________
18. For each of the following complete and balance the reaction. Also write the net ionic equation.
a) NaOH + HBr net ionic equation: _________________________
b) KOH + HClO4 net ionic equation: _________________________
c) Al(OH)3 + HCl net ionic equation: _________________________
d) LiOH + H2SO4 net ionic equation: _________________________
e) V(OH)3 + H2SO4 net ionic equation: _________________________
19. What volume of 0.185 M HCl would be needed to neutralize 34.56 mL of 0.235 M KOH? _________
20. What volume of 0.350 M LiOH would be needed to neutralize 23.81 mL of 0.125 M H2SO4? ________
21. It takes 13.67 mL of 0.0750 M HNO3 to neutralize 25.67 mL of NaOH solution. What is the [NaOH]? _________
What was the original pH of the NaOH soln? ________ What was the pH once it had been neutralized? _________
22. It takes 65.92 mL of Ba(OH)2 soln to neutralize 45.22 mL of 0.115 M HBr. What is the [Ba(OH)2]? ________
23. Will the resulting mixtures be acidic, basic or neutral? For a real challenge, determine the pH of the mixtures:
a) 25.0 mL of 0.0175 M HBr & 35.0 mL of 0.0132 M KOH. _________ pH = ________
b) 65.0 mL of 0.00750 M HBr & 45.0 mL of 0.00947 M KOH. _________ pH = ________
c) 42.0 mL of 0.0236 M HBr & 89.0 mL of 0.0112 M KOH. _________ pH = ________
0.0394 0.399 1.426
2.426 2.53 3.25 3.426
7.00 9.63 10.61 11.76
12.60 17.0 43.9 77.3
95.0 acidic basic
L M mg mL mL 35
Titration Lab Name: ________________ partner_______________ Purpose: To determine the molarity of a NaOH solution by performing a titration using 0.250 M HCl. Procedure: 1. Obtain about 60 mL of 0.250 M HCl solution in a 100 mL beaker. Rinse the “red” buret with about 5 mL of this solution. Pour into sink. Repeat once more, then fill the buret all the way with the HCl solution. Put the buret back in the buret clamp.
2. Place the plastic cup labelled “waste” under the buret and open the stopcock to allow any air bubbles to escape from the buret. Then fill the HCl buret to between the 0 and 10 mL mark.
3. Record the precise level of the HCl in the table below: Trial 1 (remember to use the black stripe and read from the bottom of the meniscus. (example: 23.48 mL, see Figure at right)
4. Obtain a blue dot beaker and carefully measure _______ mL of solution B1 and ________ mL of solution B2 into it. Use a plastic pipet to mix this up thouroughly! This will give you a NaOH solution of unknown concentration. Call it X M NaOH. Your objective in this lab is to solve for X, and since each lab group has a unique volume combination of these two solutions, each group will have a different value for X (so don’t try using someone else’s correct value for X!)
5. Repeat steps 1-3 above placing your X M NaOH in the “blue” buret. Again record the NaOH level in the table below.
6. Place the Erlenmeyer flask under the HCl buret, open the stopcock and allow 10 -12 mL of the HCl to flow into the flask. Then close the stopcock. Add 2 drops of the phenolphthalein indicator to the HCl in the flask.
7. Place the Erlenmeyer flask under the NaOH buret and open the stopcock to allow approximately 5-8 mL of the NaOH to flow into the flask while continuously swirling the flask. Observe the color changes occurring. Continue to add the NaOH slowly while swirling the flask. When a faint pink color appears and persists for 10 seconds or more while swirling the flask, you have reached your endpoint. Note: It is important to realize that if you accidentally pass your endpoint, you can add a little more HCl to the flask which will cause the solution to become colorless again. You can then add the NaOH slowly to the flask again and attempt once more to carefully reach the endpoint. This is known as “back-titrating.”
8. When you have reached the endpoint, record both of the HCl and NaOH final buret readings in the table below (again to the bottom of the meniscus and again to the hundredth of a mL).
9. Calculate the molarity of the NaOH solution, showing your work in the space provided below.
10. Pour the faint pink solution out of the flask (into the sink) and repeat the titration again-- no need to rinse the flask, only this time using 13-15 mL of the HCl solution. Don’t forget to record the initial levels – they should be the final levels from the previous trial unless you had to add some more solution. You should estimate how much NaOH you will need for this titration based on the information that you gathered from the first titration. (Think proportions… ) This will let you get very close to the endpoint… then go drop-wise to get the precise end-point.
11. Calculate the molarity of the NaOH solution from the second trial. Is it close to the results from your first trial?
12. Repeat steps 10 and 11 above for a third and final trial. If your three values are all pretty close then average them. If there is an obvious outlier, then throw it out if you want to. It’s up to you, but when you have finished, bring it up to the instructor. Since he knows the concentrations of B1 and B2, he can quickly determine, based on the two volumes above,
the NaOH concentration you were supposed to get. You will be graded on your accuracy of your final answer, so do a careful job – with the original mixing, with the titration, and with the calculations!
MOLARITY OF NaOH: (watch sig figs & units!) Trial 1: _______ Trial 2: _______ Trial 3: ________ Final Answer:
Trial 1 HCl NaOH
Trial 2 HCl NaOH
Trial 3 HCl NaOH
Data Table: Initial buret reading (mL)
Final buret reading (mL)
Total volume used (mL)
Calculations: Show all work below, then write your results on the top of the back side.
23
24
mL
36
FOLLOW UP QUESTIONS: (these have been made into a quia for you (of course) 1. Write the balanced equation for the reaction that took place in this lab. 2. This reaction could be categorized as a _______________________ reaction or as a _________________________________ reaction. 3. Consider each of the following potential error sources. Answer: “H” if it would have caused your calculated value for X M NaOH to come out too high, “L” if it would have caused it to come out too low, or “N” if it would have had no effect at all on your value.
_____ You added 3 drops of phenolphthalein instead of 2 drops.
_____ An air bubble was present in the HCl buret, but it stayed in while you titrated.
_____ An air bubble was present in the HCl buret, and it came out while you titrated.
_____ There was a pebble in the bottom of the NaOH buret during the entire titration.
_____ You forget to add the phenolphthalein indicator.
_____ While you were titrating, some NaOH dripped out onto the table instead of into the flask.
_____ There was a little distilled water in the Erlenmeyer flask before you began the titration.
_____ There was a little HCl in the Erlenmeyer flask before you began the titration.
_____ There was a little distilled water in the HCl buret and you forgot to rinse it out with the HCl.
4. Why did you rinse the buret with the solutions first? 5. Why did you use burets instead of graduated cylinders to do this lab? 6. Why did you not have to rinse out the flask in between trials? ADDITIONAL PROBLEMS: 7. You are given a solution of 0.100 M HCl as was used for this lab and are again told to find the unknown molarity of a different NaOH solution. You start with 10.54 mL of HCl and need 13.17 mL of NaOH to reach the endpoint. What is the molarity of this NaOH solution? Ans: ________ 8. You are now given a solution of 0.170 M NaOH and are told to find the molarity of an unknown HBr solution. You start with 11.29 mL of NaOH and need 38.55 mL of HBr to reach the endpoint. What is the molarity of the HBr? Ans: ________ 9. How many mL of 0.340 M HCl would be needed to titrate 14.91 mL of 0.265 M NaOH? Ans: ________ 10. How many mL of 0.340 M HCl would be needed to titrate 14.91 mL of 0.265 M Ca(OH)2? Ans: ________ 11. Complete this statement: (10 bonus points for the most creative... and appropriate) Doing a titration without an indicator is like ____________________________________________________________.
Grading scale
Within 0.003 M = 20pt Within 0.005 M = 19pt Within 0.007 M = 18pt Within 0.009 M = 17pt Within 0.011 M = 16pt Within 0.015 M = 15pt Within 0.019 M = 14pt Within 0.025 M = 12pt Within 0.030M = 10pt Within 0.040 M = 8pt Within 0.050 M = 5pt If not… 2 pt for showing up
37
Brainstorming on Gases Note-sheet Name: _________________________
1. What do gases have in common with liquids?
How are they different?
2. Describe how gas molecules move.
3. What is “volume” as it pertains to a gas sample?
What piece of equipment is used to measure the volume of a gas sample?
What units are used for measuring volume?
4. What is “temperature”?
What piece of equipment is used to measure temperature, and how does it work?
What units are used for measuring temperature?
Why “degrees”? Mass is measured in “g,” energy in “J;” why can’t temperature just be measured in “C”?
5. What is “pressure” as it pertains to a gas sample?
What piece of equipment is used to measure pressure, and how does it work?
What units are used for measuring pressure?
6. How do temperature and volume relate— direct or inverse? Explain why.
7. How do temperature and pressure relate— direct or inverse? Explain why.
8. How do pressure and volume relate— direct or inverse? Explain why.
9. Explain how a drinking straw works.
38
Gas Laws Tutorial Notesheet. Name: __________________ __ 1. Describe gas particles’ spacing and movement a) far apart & standing still (not moving at all) b) close together & vibrating slowly in place c) far apart & vibrating rapidly in place d) close together & swirling around each other e) far apart & bouncing around randomly
__2. In terms of the particles, what exactly is temperature a measurement of? a) how hot the particles are all together c) the total kinetic energy of all the particles put together b) the average hotness of all the particles d) the average kinetic energy of the particles e) whether the particles are running a fever or not
__3. In terms of the particles, what exactly is pressure a measurement of? a) the collective force exerted by the particles as they collide with the walls of the container b) the collective force exerted by the particles as they repel outward away from one another c) the pulling force created by a vacuum against a gas samples particles d) the amount of stress and strain the particles feel from their parents and from their peers
__4. In terms of the particles, what exactly is volume a measurement of? a) the sum of all the particle sizes added together b) the total amount of surface area taken up by the particles c) the amount of space the particles are allowed to occupy d) how loud the particles are as they smack against each other
5. In the diagram, what would be your reading for the volume of the gas sample?______
__6. As the blue wall moves up and down, what property of the gas sample is changing? a) temperature b) pressure c) volume d) all of the above e) none of the above
__7. If the wall is being pushed up by the pressure of the gas sample, why is it not moving upward? a) the pressure is not strong enough b) the particles are pulling as much as they are pushing c) the air outside the container is exerting an equal pressure downward on the wall d) the wall is made from a material that is not affected by pressure.
__8. If the gas sample were heated up to 600 K, the particles would be... a) moving faster b) moving slower c) melting d) expanding e) vibrating quickly in place
__9. What else would change about the sample? a) the volume would increase b) the volume would decrease c) the pressure would increase d) the pressure would decrease
__10. Why does increasing the temperature increase the pressure? a) the particles are hitting the walls more often b) the particles are hitting the walls harder c) the particles are hitting the walls harder and more often d) the container is too hot for the particles so they feel added pressure to try to escape.
__11. If the temperature were increased to 1800 K, what would the new pressure be? a) 1. 0 atm b) 2.0 atm c) 3.0 atm d) 6.0 atm e) 12.0 atm
__12. If the temperature were decreased to 900 K, what would the new pressure be? a) 0.5 atm b) 1.0 atm c) 3.0 atm d) 6.0 atm e) 12.0 atm
13. Write down Gay-Lussac’s equation for the relationship between pressure and temperature:
14. A gas starts at 900 K & 3.0 atm. It is then changed to 629 K. Using Gay- Lussac’s equation, write the correct set-up to solve for the new pressure:
15. What do you get when you solve this for P2? __________
16. A gas sample has a pressure of 1.26 atm at 31°C. What pressure would it exert at 64°C? Write the correct set-up to solve this problem:
17. What do you get when you solve this equation? __________
39
18. A sample of neon has a pressure of 725 torr at 143°C. What pressure would it have at -19°C? Write the correct set-up to solve this problem:
19. What do you get when you solve this equation? __________
20. At 26°C, a flask of CO2 gas exerts a pressure of 34.8 psi. To what temp (°C) must it be changed to increase the pressure to 45.9 psi? Set-up:
21. What do you get when you solve this equation? __________
22. What is the final answer to the question posed in #20 above? __________
23. On the axes at right, sketch what you think a graph of P vs T would look like: __24. If the pressure were increased, the gas sample’s volume would _____. a) increase b) decrease c) stay the same
__25. The sample started off with a volume of 2.0 L. If the pressure was increased from 1.0 atm to 2.0 atm, what will the new volume end up at? a) 0.25 L b) 0.5 L c) 1.0 L d) 1.5 L e) 2.0 L
__26. The sample starts off with a volume of 2.0 L. If the pressure is decreased from 1.0 atm to 0.5 atm, what will that change the volume to? a) 0.5 L b) 1.0 L c) 2.0 L d) 3.0 L e) 4.0 L
27. Write down Boyle’s equation for the relationship between pressure and volume:
28. At 2.05 atm, a methane sample has a volume of 31.5 L. What volume would it have at 6.24 atm? Set-up:
29. What do you get when you solve this equation? __________
30. 23.5 mL of He gas are at 726 torr. What volume would the He occupy at 715 torr? Set-up:
31. What do you get when you solve this equation? __________
32. At 13 psi, a sample of O2 fills a 3.9 L balloon. What pressure would compress it down to 2.7 L? Set-up:
33. What do you get when you solve this equation? __________
34. On the axes at right, sketch what you think a graph of V vs P would look like:
__35. 2.0 L of gas are at 1.0 atm and 300 K. Keeping the pressure constant at 1.0 atm, if the temperature were raised to 600 K, what will the new volume be? a) 0.5 L b) 1.0 L c) 2.0 L d) 4.0 L e) 8.0 L
__36. 4.0 L of gas are at 600 K. If the temperature were decreased to 200 K, what will the new volume be? a) 0.5 L b) 1.0 L c) 1.3 L d) 2.0 L e) 12.0 L
__37. How do temperature and volume vary? a) directly b) indirectly c) versely d) inversely
38. What would the equation for temperature and volume look like?
39. A sample of nitrogen has a volume of 23.8 mL at 24°C. What volume would it have at 12°C. Set-up:
40. What do you get when you solve this equation? __________
41. The syringe shown in the tutorial contains some helium gas at -18°C. What will the syringe reading change to at 142°C? Set-up:
42. What do you get when you solve this equation? __________
P
T
V
P
40
43. A hydrogen-filled balloon has a volume of 2.5 L at 25°C. It is then placed in a freezer and the volume decreases to 1.9 L. How cold (in °C) is the freezer? Set-up:
44. What do you get when you solve this equation? __________
__45. Why is “226 K” not the final answer? a) too many sig figs b) too few sig figs c) wrong units d) because it’s just way too high
46. What is the correct final answer to #43 above? __________
47. On the axes at right, sketch what you think a graph of V vs T would look like:
48. Take a guess, what do you think the equation looks like that combines all six of these variables: P1, V1, T1, P2, V2, and T2?
49. A sample of helium gas has a volume of 75.0 mL at 38°C and 2.94 atm. What volume would it have at 89°C and 2.36 atm? Set-up:
50. What do you get when you solve this equation? __________
51. A sample of fluorine gas in a 3.78 L bottle at 22°C exerts a pressure of 569 torr. What pressure would it exert in a 1.00 L flask at 114°C? Set-up:
52. What do you get when you solve this equation? __________
53. A 55 gal tank is filled with argon gas at 25°C & 35 psi. This gas is then transferred to a 75 gal tank which is only strong enough to withstand an internal pressure of 67 psi. At what temp (°C) would the tank explode? Set-up:
54. What do you get when you solve this equation? __________
55. What is the correct answer for #53 above? ___________
56. A helium balloon has a volume of 2.35 ft3 at 25°C. It is then taken the top of a mountain (-5°C and 725 torr), and the volume changes to 2.18 ft3. What must the original pressure have been? Set-up:
57. What do you get when you solve this equation? __________
V
T
41
PVT WS The relationships between pressure, volume & temperature for samples of gases Name: _________________
1. Temperature and volume vary ________________. In other words, as one increases the other _______________,
and as one decrease, the other _________________. This is known as _____________ Law. When using the equation
(V1/T1 = V2/T2) ______________ can be in any units (L, mL, ft3....), but ________________ must be in _____ and never
in ____.
2. Volume and pressure vary ________________. In other words, as one increases the other _______________, and as
one decreases, the other _________________. More specifically, if pressure doubles, then the volume
_______________, and if the pressure is cut to one-third, then the volume is________________. This is known as
_____________ Law. _____________ is the amount of space a gas sample occupies (but most of that space contains
__________.) _____________ is the sum of all the collision forces as the
______________ bounce off the walls of their container.
3. Temperature and pressure vary ________________. This is known as _____________ Law. ______________ is a
measurement of the average kinetic energy of the ______________ . When the temperature increases (with
_______________ held constant), the pressure _______________ because the
particles are hitting the walls _______________ and more ________________.
4. For each of the following, choose the Law (a = Gay-Lussac, B = Boyle, C = Charles) that best explains the situation.
___ An canister of compressed air explodes when it was left in the trunk of a car on a very hot day.
___ A helium filled mylar balloon appears to deflate a little when taken outside in January
___ The flight attendant gave Jenny a Dorito bag that was so puffed up she decided to keep it and
show it to her friends back home. Later, when she took it out to show them, it was just normal.
___ Joe was using one of those upside ketchup bottles and forgot to put it back in the fridge.
When he went to open it, the ketchup went all over the place.
___ In the late Fall, Allen adds some extra air to his tires, just so they’ll stay at the right pressure.
Then in the Spring, he lets some air back out for the same reason.
___ Marshmallows heated in the microwave oven grow really big!
___ When a small, air-filled balloon was put in the bell-jar, it tripled in size.
___ A scuba diver blows a regular sized bubble 70 m below sea level,
but by the time the bubble reaches the surface, it is humungous!
The following problems are meant to be done in your head:
5. A hydrogen tank has a pressure of 60.0 psi at 200 K. What pressure would it have at...
a) 400 K? ______ b) 100 K? ______ c) 600 K? ______ d) 50 K?______ e) 2000 K ______
6. A fluorine sample has a volume of 12.0 L at 300 K, what temp (K) would change its volume to...
a) 6.0 L? ______ b) 36.0 L? ______ c) 2.0 L? _____ d) 60.0 L? ______ e) 4.0 L? ______
7. A helium balloon has a volume of 18 mL at 600 torr. What volume would it have at...
a) 300 torr? _____ b) 1800 torr? _____ c) 100 torr?_____ d) 6000 torr? _____ e) 6 torr?_____
Boyles
*C K
Charles
cut to one-half
decreases
decreases
directly
directly
Gay-Lussac
harder
increases
increases
increases
inversely
nothing
often
particles
particles
pressure
temperature
temperature
triples
volume
volume
volume
A A A B B C C C
1.8 6.0 15.0 30.0 36 50.0 100 108 120 150 180 600 900 1500 1800 5(psi) 5(K) 5(mL)
42
Show work for the remaining problems: The only equation you need is: =
8. At 35*C, a CO2 sample has a volume of 23.4 mL. What volume would it have at 22*C? Ans: ________ 9. At 2.14 atm a He sample takes up 4.15 m3. How much space would it take up at 6.72 atm? Ans: ________ 10. In a rigid jar at 57*C, some Ne exerts a pressure of 840 torr. What pressure would it exert at 1560*C? Ans: ________ 11. A bag contains 45.9 L of gas at 15.2 psi. What pressure would expand the gas to 23.7 L? Ans: ________ 12. A tank of N2 gas has a pressure of 135 atm in a freezer. At 25*C the pressure is 157 atm. How cold (*C) is the freezer? Ans: ________ 13. A balloon has a volume of 27.8 L at 312 K. To what temp (K) must it be cooled to shrink it down to 25.6L? Ans: ________ Ans: -100 -17 0.643 1.32 4.38 9.44 13.3 22.4 27.2 29.4 269 287 488 4670 Units: *C *C *C psi psi psi mL mL m3 torr torr atm K
14. At STP (standard temperature and pressure, which is 0*C and 1.00 atm), a sample of fluorine gas has a volume of 32.8 mL. What would the volume change to at 26*C and 1.32 atm? Ans: ________ 15. If a sample of O2 has a pressure of 67 psi in a 2.5 L tank at 25*C, what pressure would that same sample have in a 35 L tank at 0*C? Ans: ________ 16. If the pressure on 38.0 mL of N2 is 785 torr at 22*C, and then the pressure changes to 725 torr, what temperature (*C) would be required to reduce its volume to 24.1 mL? Ans: ________ 17. A sample of neon has a volume of 75.4 mL at STP. It is then placed in a 95.0 mL chamber at a temperature of -52*C. What pressure would it exert? Ans: ________ 18. Carbon monoxide is placed in a 3.40 m3 tank at 156 psi and 24*C. What temperature (*C) would be needed to increase the pressure to 285 psi? Ans: ________
43
PV = nRT WS R = 62.4 L torr/mol K or 0.0821 L atm/mol K or 8.314 L KPa/mol K Name: ____________________ 1. What volume would 3.00 moles of neon gas have at 295 K and 645 torr?
Ans: ______
2. What volume would 4.3 moles of hydrogen gas occupy at 45*C and 3.22 atm?
Ans: ______
3. How much pressure would 4.85 moles of He gas exert in a 4.50 L tank at 31*C?
(use either R value) Ans: ______
4. How many moles of CO2 could fit in a 475 mL bag at -22*C and 855 torr?
Ans: ______
5. 0.173 moles of argon gas are placed in a 2.50 L tank. What temperature (*C)
would be needed to create a pressure of 1.78 atm?
Ans: ______
6. How many moles of He can fit inside a 569 L tank at 748 torr and -34*C
Ans: ______
MOLE CONNECTIONS
7. How many grams of C2H6 gas are there in a 2.3 L tank at 7.5 atm and 24*C?
Ans: ______
8. How many molecules of N2 could fit in a 2.00 L soda bottle at 23*C and 755 torr?
Ans: ______
9. How much space would be taken up by 3.40 x 1024 molecules of NO2 gas at 798 torr & 128*C?
Ans: ______
10. What pressure would be required to fit 35.0 g of N2 gas into a 195 mL flask at 0*C?
Ans: ______
0.0259 21.2 26.9 28.5 35 40 85.6 144 177 20,400 109,000 4.92E22 units: L L L mol mol g atm atm torr *C torr molecule
44
11. What volume would be occupied by 16.0 g of CH4 at 0*C and 760 torr?
Ans: ______
12. How much space would be taken up by 2.5 g of CO2 gas at 523 K and 0.85 atm?
Ans: ______
DENSITY
13. a) What is the mass of 1.00 mole of neon? b) What would be the volume of 1.00 mole of neon at 34*C
and 655 torr? c) What would be the density of 1.00 mole of neon at 34*C and 655 torr?
a: ______ b: ______ c: ______
14. a) What is the mass of 2.00 moles of neon? b) What would be the volume of 2.00 moles of neon at 34*C
and 655 torr? c) What would be the density of 2.00 moles of neon at 34*C and 655 torr?
a: ______ b: ______ c: ______
15. What is the density of helium at 2.15 atm and -45*C?
(Hint: assume there’s 1.00 mole) Ans: ______
16. Determine the density of fluorine gas at 595 torr and 423 K.
Ans: ______
STOICHIOMETRY
17. How many moles of sodium will react with 2.6 L of Cl2 gas at 1.15 atm and 39*C?
Hint: use the balanced equation is 2 Na + Cl2 2 NaCl Ans: ________
18. How many grams of propane will react with 3.29 L of O2 at 796 torr and -34*C?
Hint: balance the equation, then use it: ___C3H8 + ___O2 ___CO2 + ___H2O
Ans: ______
19. BONUS What volume of oxygen gas at 29*C and 1.55 atm will react with 2.67 g of Al? Hint: Write, balance & then
use your own equation!
0.23
0.459
0.692
0.692
0.857
1.19
1.54
2.9
20.2
22.4
29.2
40.4
58.4
units:
g/L g/L
g/L g/L
g g g g
L L L L
L mol
45
ABSOLUTE ZERO LAB: How low can you go? Name: __________________ Partner: _________________ The temperature of a gas sample is a measurement of how fast the particles in that sample are moving. (More precisely, it’s a measurement of the average kinetic energy of the particles). As we heat up a gas sample, its particles move faster and faster (the kinetic energy increases), and as we cool it down, the particles move slower and slower (the kinetic energy decreases). If that is true, it only stands to reason that there must be a lower limit to the temperature scale, a temperature where the particles have stopped moving all together! And one could never get anything colder than that temperature, for if the particles have stopped moving, they obviously can’t move any slower. This minimum temperature does in fact exist, and it is called absolute zero. Certainly, the Celsius scale is not an absolute scale, for one can easily reach temperatures below zero degrees Celsius. 0°C is just the temperature where water freezes, and even when water freezes, its particles are still vibrating at hundreds of miles per hour! You would have to cool something down a lot further to get its particles to stop moving all together. Most people have heard of liquid nitrogen and consider it to be very cold, and it is: -196°C. Nonetheless, even at this low temperature, particles still have quite a bit of kinetic energy left. So how low do you have to go to reach absolute zero? Even though we can’t get that low, we can determine how low that temperature is in a rather simple way: First, remember that a gas sample is mostly empty space. The particle themselves are so small, we can pretty much ignore their size. It is the space between the particles that accounts for 99.9% of a gas’s volume. And what keeps this space between the particles is the fact that the particles are constantly moving around and bouncing off one another. As the sample cools down, and the particles slow down, it should be easy to see that they would not create as much space between them, and so the volume would decrease. It follows then that if we can cool a gas down far enough so that the particles stop moving, we could get rid of all of the space between the particles and the volume would become essentially zero. We can’t get that cold, but we can measure the volume of some gas samples at a high temperature and then measure their volumes again at lower temperature. We can then plot these data and extrapolate backwards to determine approximately how cold we would have to get the samples to make their volumes zero.
Procedure:
1. Obtain three syringes, (A) filled with a large volume of N2, (B) filled with
a medium volume of N2, and (C) filled with a small volume of N2.
2. Hold all three of them in the cold water bath submerged just to the plunger
(as shown at right) for 1 minute. While still in the cold water, push down on
the plunger and release. Take a volume reading when the plunger stops
moving. Repeat this for each of the three syringes. Also, take a temperature
reading. Record these in the table below.
3. Repeat step 2 in the warm water bath, and then again in the hot water bath.
Data Table:
Treatment of the data:
Plot your temperature and volume measurements on the graph provided. Plot all the data on the same graph, but use
different symbols for A, B and C (for example, use an O for A, an X for B and a ∆ for C -- plot these points as precisely as
possible). Look at the data points for sample A, they should show a high volume at the high temperature, a medium
volume at the middle temperature and a small volume at the low temperature. Draw a best fit straight line (use a
straight edge) through these three points. Then extend (extrapolate) this line backwards to determine how cold you
would have to get that sample to cause its volume to be zero. Repeat this technique with samples B and C. Then
answer the questions below.
Volume (mL)
Temp (°C) A B C
in cold water
in warm water
in hot water
46
1
2
3
4
5
3.7 mL
Questions:
1. As the temperature of a gas sample increases, its volume ___________. This is known as _____________ Law.
2. Why does this happen (explain based on the behavior of the gas particles)?
3. What is temperature?
4. Why must there be a bottom to the temperature scale?
5. What happens to the particles at this bottom temperature?
6. Why did you submerge the syringe as far as you did in the water baths?
7. What caused the syringe plunger to get pushed outward at higher temperatures (explain this in terms of what the
behavior of the gas particles inside and outside the syringe)
8. What do you think would have happened if the syringe had not been sealed shut?
9. What does the word extrapolate mean? _________________________________________
10. Based on your graphs and extrapolations, what value did you get for absolute zero...
for sample A? __________ for sample B? __________ for sample C? __________
11. What was your average value for absolute zero? __________
12. What is the accepted value for absolute zero? _________
(13. In addition to extrapolating, you can also interpolate from your data: for example, what volume would each of the
samples have had at 32.0°C? A? _________ B? __________ C? __________ )
14. Scientists have devised a scale called the Kelvin scale (K) based on setting the accepted absolute zero value equal to
0 K, but using the same size unit as the Celsius scale. So what would 0°C be on the Kelvin scale? ________ How about
100°C? ________ 22°C? ________ -196°C? ________
15. Which is a more appropriate temperature scale to use, Kelvin or Celsius? ____________ (Hint: Consider what
temperature is a measurement of.) Explain your choice:
47
16. How do you think the size of the molecules would have affected the value you got for absolute zero? In other words,
if you had used, for example, helium instead of nitrogen, how would your results compare? (Hint: reread the opening
paragraphs.)
17. As a gas sample is cooled toward absolute zero, what happens to the...
particles’ average velocity? ____________________________________________
spacing between particles? ____________________________________________
pressure exerted by the particles? ____________________________________________
mass of the particles? ____________________________________________
volume of the gas sample? ____________________________________________
density of the gas? ____________________________________________
attractive forces between the particles? ____________________________________________
18. Scientists can cool substances down to near absolute zero (even as low as 0.00001 K), but they have never actually
reached absolute zero (0 K). Why do you suppose that is?
19. The data below are not very good, but plot them any- way and then use them to derive an experimental value (in°C) for absolute zero. (You will need to scale & label the axes for yourself!)
20. In no more than fifty words and no less than one diagram, describe precisely what the lab was all about: what you
did and why you did it.
21. List three major error sources that might have caused your absolute zero value to be off.
volume of gas Temp (°C) sample (mL) 5.0 7.2 20.0 7.7 60.0 9.2 90.0 10.0
48
-350
-340
-330
-320
-310
-300
-290
-280
-270
-260
-250
-240
-230
-220
-210
-200
-190
-180
-170
-160
-150
-140
-130
-120
-110
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
90
100
110 49
Boyle’s Law Lab: Pressure vs. Volume Name: __________ Partner: _______ One thing that you may have already learned about gases is that as temperature increases, the average speed of the particles increases. They collide harder and more often and thus push away from each other, causing the volume to increase. Charles’ Law states: with pressure held constant, temperature and volume vary directly. A graph of volume (in mL) vs. temperature (in Kelvins) would be a straight line, passing through the origin, as shown at right: From the reading, and from class discussion, you have probably come to appreciate that pressure and volume do not vary directly; as the pressure on a gas sample increases, the volume decreases (and vise-versa). Think about pushing in on the plunger of the closed-end syringe: the more pressure you apply, the smaller the volume gets. Think also about placing an air filled balloon in the bell jar and then turning the vacuum pump on to pump air out. As the pressure in the bell jar decreases, the volume of the balloon increases. Boyle’s Law states: with temperature held constant, pressure and volume vary inversely. How do you think a graph of volume as a function of pressure would look? Right now, sketch your idea on the axes at right: In this lab, you will examine this inverse relationship by subjecting a sample of air to a variety of pressures. You will also use the data you collect to determine the air pressure in the room. Procedure: 1. Obtain a pressurized soda bottle from the instructor. Notice that inside the bottle is a closed-end syringe with a trapped volume of air. What do you predict would happen to this volume if some of the pressure is let out of the bottle? Use the nub on the backside of the gauge to push down slightly on the center of the valve stem until the piston in the syringe just barely starts to move. Was your prediction correct? 2. Use the tire gauge to take a pressure reading. To do this, press the gauge quickly and securely against the valve stem, allowing the incremented bar to shoot out freely from the open end. If you accidentally block the bar, press it in and try again. Also, do not press the gauge lightly against the stem... this will just let out air and will not give an accurate pressure reading. The measurement must be quick and deliberate. Record the gauge pressure in the table below. 3. Now take a precise volume reading of the air in the syringe: make sure you are reading at the correct place as shown at right. Record this volume in the table below, alongside the corresponding pressure gauge reading. 4. Again press down lightly on the center of the valve stem to let some more air out: this time enough to make the volume of the syringe change by about 0.5 - 0.7 mL. Reset the pressure gauge by sliding the bar back inside, then repeat steps 2 and 3 above. 5. Repeat this process three more times to get a total of five pressure / volume readings. If you mess up, simply have the bottle re-pressurized and try again. Graph #1 (V as a function of P): On the back-side, recopy these data in the table provided; then plot the data points using the x-axis for gauge pressure and the y-axis for air volume. You will have to decide how best to scale the axes, but have the origin be 0, 0 and plan it out so that the data fill the graph as much as possible. Don’t forget to label your axes with the variable and the units [example time (s)], and to title the graph. Once the points are plotted, draw a best fit straight or curved line, whichever seems appropriate. (DO NOT DO A CONNECT-THE-DOT). How accurate were you at predicting the shape of the line?
temperature
volume
volume
pressure
These volumes should be different by at least 0.5 mL each. (for example, 2.9, 3.6, 4.5, 5.2... If they’re not, go back and re-read procedure step #4!
gauge pressure
(psi)
air volume
(mL)
DATA TABLE
1
2
3
4
5
3.7 mL
50
Calculations: One way of stating mathematically that two properties vary inversely is to say that their product is a constant (that when you multiply the two values, you always get the same number: in other words: P1 x V1 = P2 x V2 = P3 x V3 ....). Recopy your data from the front side onto the table below and then calculate the products, writing them in the spaces provided: How consistent are your results (that is, how much did P x V stay constant)?
The reason your results were not consistent was because of the tire gauge. The pressure values it shows are not actual pressures, they are relative pressures. The gauge tells you how many extra psi were in the bottle, above and beyond the air pressure around the gauge. Consider for example what the gauge would report the pressure to be if you connected it to a flat tire or to a bottle that were not pressurized at all. It would read “0 psi”. Yet we know there is not a vacuum inside; there is just normal atmospheric pressure (about 14.7 psi, that’s considered standard pressure). Thus a pressure gauge reading of 10.0 psi means the pressure inside is actually about 24.7 psi. And when you inflate your car tires to the recommended 30.0 psi, you are actually inflating them to about 44.7 psi. That means all your pressure gauge readings in the lab are too low, by about 14.7 psi. Rather than saying “about 14.7 psi” for atmospheric pressure, let’s call it “X” and use some of your data lines above to get an experimental value for X. If, for example, your first and second data lines looked like the ones at right, you would have already noticed that P1V1 didn’t equal P2V2. But that’s because the P values were both too low by an amount X. If we set up the equality incorporating X, we have: (48.0 + X) x 2.0 = (24.5 + X) x 3.1 which distributes out to: 96 + 2.0X = 76 + 3.1X Combining like terms gives: 1.1 X = 20, which simplifies to X = 18 psi (pretty close to the accepted value of 14.7 psi). Repeat these calculations below using your data. First, do this calculation using the first and second data lines as shown above, then repeat the calculation using the first and last data lines: (Which calculation do you think will give better results?
first and second data lines: first and last data lines: Ans: _____ Ans: _____
gauge pressure
(psi)
air volume
(mL)
P x V (psi
·mL)
gauge pressure
(psi)
air volume
(mL)
P x V
(psi·mL)
48.0
24.5
2.0
3.1
96
76
11 51
Title:
Graph #2 (1/V as a function of P) You may be wondering at this point whether you can derive a value for atmospheric pressure from all the data at once by using some graphing technique. It turns out that you can. You discovered that the graph for V as a function of p gives a curve like the one shown at right (A). Again, this is known as an inverse relationship. But what about the inverse of V (that is, 1/V) as a function of P? That graph turns out to be a straight line that passes through the origin as shown in the second graph at right (B). But what about a graph of 1/V as a function of P in which all the P values were too low by a constant amount x? That would simply shift the line to the left by precisely x, so that instead of intercepting the x-axis at the origin (0,0), it would intercept it at the point (-x,0) as shown in graph C at right. So, copy the data once more in the table below, and this time calculate 1/V for each volume (for instance, if V = 2.5 mL, then 1/V would equal 1/2.5 = 0.40. Then on the graph below, plot 1/V as a function of the gauge pressure. Draw a best-fit straight line through the data, and extrapolate it backwards to see where it crosses the x-axis. This value represents the correction factor for the gauge pressure readings. In other words, this value represents the negative of the atmospheric pressure. If, for example, the line crosses the x-axis at -13.2 psi, that would imply an atmospheric pressure of 13.2 psi, and if 13.2 psi were added to each gauge pressure reading, it would shift the entire graph to the right and allow it to pass through the origin. Based on your graph, what value do you get for the atmospheric pressure? ______
Title:
0.10
0 -20 -10 0 10 20 30 40 50
gauge pressure (psi)
A B
C
V
P
1/V
P
-x
V
1/V
P
12
gauge pressure
(psi)
air volume
(mL)
inverse of air volume
(1/mL)
52
0.20
0.30
0.40
Questions: 1. When some of the pressure was released from the bottle, the syringe plunger moved up. Why did this happen? And don’t just say: “because the pressure decreased...” Explain why this happens in terms of the gas particles moving around inside and outside the syringe before and after the pressure was released! USE DIAGRAMS. 2. Why does the pressure gauge only give relative pressures? Why can it not give actual pressures? 3. If the gauge reports “67.0 psi” for your bicycle tire, what is the actual pressure in the tire? _____ (Assume standard atmospheric pressure) 4. Use the data table at right to reproduce your first & second, and first & last calculations for the lab: first and second data lines: first and last data lines: Ans: _____ Ans: _____ 5. Most students find that they get much better results (closer to 14.7 psi) when they use their first and last data lines rather than their first and second, or second and third... Why do you suppose that is? 6. If the gas sample had a volume of 2.7 mL at a gauge pressure of 41.5 psi, what volume should it have at a gauge pressure of 18.6 psi. (Assume standard atmospheric pressure = 14.7 psi) Ans: _____ 7. If the pressure gauge reported values in torr instead of psi, and the gauge reading for the bottle was 1250 torr, what would the actual pressure be (in torr)? Ans: _____ 8. Tire manufacturers often warn customers to let air out of their tires in the spring. Why? Again, explain using diagrams, in terms of what the gas particles are doing.
gauge pressure
(psi)
air volume
(mL)
46.0
25.2
2.3
3.2
18.3
14.6
4.3
4.6
11.7 5.2
53
R Lab Name: _______________________ You have learned that “R” is the gas law constant that relates a gas sample’s pressure, volume, number of moles and temperature. Given any three of these properties, R allows you to determine the value of the fourth. But how is R itself determined? In this lab you will measure – directly or indirectly – P, V, n and T, and then use them to determine an experimental value for R. To do this you will use a chemical reaction that produces a gas – then use stoichiometry to determine the number of moles of the gas, collect this gas in a long incremented test tube – so you will know the volume of the gas, look up the current local barometric pressure and make the necessary adjustments on it to determine the pressure of the gas, and of course use a thermometer to measure the temperature of the gas. Procedure: 1) Obtain a piece of magnesium ribbon, and use a metric ruler to measure very precisely its lengths (top and bottom) in cm. Record these in the data table below. Then roll the ribbon up into a small coil as shown at right. Loop a small wire through the coil and pass the other end of the wire through the hole in the small end of a rubber stopper. Set this aside. 2) Holding the bottom end of gas collecting tube in the sink to catch any spillage, carefully add about 8-10 mL of 3 M HCl solution. Then add tap water on top of the HCl all the way to the very top of the tube. Clamp this tube vertically in the buret clamp. Now insert the magnesium coil and stopper into the tube. Be sure there is no air pocket. (If there is, remove the stopper, add some more water, and reinsert the stopper.) 3) Now, carefully flip the tube over, holding the stopper in place as you do so, and place the stoppered end in the plastic cup filled with water. Then clamp the tube in this position. Observe what happens as the more dense HCl solution streams through the water – this is an effect known as schlieren.* As you are waiting for the reaction to happen, go to one of the computers and record the current reported barometric pressure. Then do the moles calculation – #1 below. 4) Once the reaction starts, observe the magnesium. Eventually enough will have reacted that what’s left may break away and float to the top. This is OK, as long as it continues to react and doesn’t get stuck on the side of the tube. Watch for this. Once the reaction is over, make a measurement of the volume – as always, use the black band to accentuate the meniscus and read from the bottom of the meniscus. Also, be careful: the scale is upside down. Record this volume in the table below.
5) Take the temperature of the water in the cup, which we will take to be the temperature of the gas. Record this in the table below.
6) Finally, measure the height of the water column beneath the gas sample in the tube. Record this in the table.
Calculations: 1) Moles: Usually to determine the number of moles of a substance, you simply weigh the sample and divide the mass by the molecular weight, but since gases have such low densities, they are almost impossible to weigh accurately. So instead, we started with a small piece of a solid – magnesium – and used it to generate a gas. So, write the balanced equation for the reaction that happens between HCl and Mg (Hint: remember: it produces a gas.)
Balanced equation: ______________________________________.
Now, calculate how many moles of gas were produced. You could have weighed the magnesium first, then simply converted grams Mg moles Mg, then used the balanced equation to convert moles Mg moles H2. If you had done this, however, you would have found that the tiny piece of Mg was so light that even on our best scale that reads to the thousandth of a gram, it wouldn’t have given us a very precise mass – probably only one or two sig figs. So instead, the length and mass of a very long magnesium ribbon were measured and this information is posted on the board. Now, take the average of the two lengths you measured, and – using the conversion posted on the board – convert from cm Mg g Mg moles Mg moles H2. This will require three factor label steps: moles H2 = _______
*schlieren = visible streaks produced in a transparent medium as a result of variations in the medium's density leading to variations in refractive index
Rrrrr Lab?
2.24 cm
2.27 cm
36
35
“35.68 mL”
26.4 cm
Length of Mg ribbon (cm) top|bottom
Volume of gas collected (mL)
Temperature of the water & gas (*C)
Height of the water column (cm)
Reported barometric pressure (inches Hg)
54
2) Pressure: There are four corrections that need to be made to get us from a reported barometric pressure (in inches of Hg) to the actual pressure of the H2 gas in the tube (in torr). A) First, convert the reported barometric pressure from inches Hg to mmHg. Use factor label: 1 inch = 25.4 mm. And since a “mm Hg” is the same thing as a “torr.” We now have reported barometric pressure in torr. Show work: Reported barometric pressure = _________ torr B) As it turns out, the reported barometric pressure is not the actual barometric pressure. (That’s right! The meteorologists are lying to us!) Reported barometric pressures have all been adjusted to sea level elevation. In other words, the reported barometric pressure in Kirkwood at a given time is what the pressure would be if Kirkwood were at sea level. (The reason for doing this will be discussed in the follow-up questions.) But Kirkwood is obviously not at sea level. KHS, for example, is at an elevation of 222 m (639 ft). As you move upward through the atmosphere, the air gets progressively thinner and thinner and this decreases the pressure by 0.0866 torr for every meter. So a meteorologist measures the pressure in Kirkwood and adds 222 m x (
0.0866 torr/1 m) = 19.2 torr to it to report what the pressure would be at sea level. So to
determine the actual barometric pressure, simply take the value from A above and subtract 19.2 torr from it. (If you had done this lab at Flagstaff High school in AZ (2114 m) you would be subtracting 183.1 torr instead Actual barometric pressure = __________ torr C) So… that’s the actual pressure in the room, but it is not the pressure inside
the gas collecting tube. If the pressures were the same, the liquid levels
inside and outside the tube would be even. Since the level inside the tube is
in fact higher, it must mean that the pressure outside the tube is greater –
enough to push the water up by ________ cm. And this is equal to
_________ mm. And since water’s density is 1 g/mL and mercury’s density is
13.6 g/mL, simply divide the mm water by 13.6 to convert this column of water
into an equivalent column of mercury: ________ mmHg
And since a mmHg is the same as a torr, subtract this number from the actual
barometric pressure in the room to get the actual pressure in the tube.
Pressure in tube: _______torr D) Finally, we would be done with all these pressure adjustments if the gas inside the tube were pure hydrogen, but since the hydrogen was collected over water, and water is always evaporating, there is a little water vapor mixed in. The pressure of that vapor (known as “vapor pressure”) is related to the temperature of the water by the graph at right. Use this graph along with the water temperature you recorded to find what the vapor pressure was inside the tube: __________ torr Now subtract that vapor pressure from the total pressure in the tube (the one derived in part C above) to determine the pressure of just the hydrogen gas in the tube Hydrogen gas pressure: ________torr 3) Volume: Easy, just convert mL into L (you should know how to do this!): Volume = ___________ L 4) Temperature: Also easy, just convert *C into K (you should know how to do this too!): Temperature = _________ K
5) R: Now that you have all the pieces… Since PV = nRT, we can rewrite this as R = PV/nT
So… calculate your PxV = ___________ L torr and your n x T = _____________ mol K. R = _______________ 6) Pooling class data. Go to the desktop computer and enter your nxT and then your PxV values. These will be graphed (PV as a function of nT). At right, sketch what you think this graph will look like. What purpose would this graph serve?
Since the water level inside the tube is higher than it is outside, that means the pressure inside must
be lower.
If the water levels were even inside and out, then the pressure inside the tube would be equal to the pressure
outside.
PV (L torr)
nT (mol K)
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19 20 21 22 23 16
17
18
19
20
21
22
23
Temperature (*C)
Vapor pressure
(torr)
Follow up questions: 1. One thing that was not mentioned was that the long piece of magnesium ribbon was buffed with piece of steel wool until it was completely shiny. Why was this important to do? 2. Should this buffing of the magnesium be done before or after the ribbon’s length and mass were measured? ________ Why? 3. The 3M HCl solution has a density of about 1.04 g/mL, and water has a density of 1.00 g/mL If the HCl had been less dense than the water, why would the procedure not have worked the same? 4. Magnesium has a density of 1.74 g/mL – which is pretty low for a metal, but still much greater than the density of the water or the HCl solution. So why did the little piece of Mg float up to the top of the tube when it broke free of the wire loop. 5. When Sammy flipped the tube over, a bubble of air somehow got in. “Oh great, he said, “Now we have to start all over!” “Oh no we don’t!” said his astute lab partner Sally… What did Sally realize they could do? 6. You repeat the entire experiment in Denver and record the following data. Determine R based on this information.
SHOW ALL WORK:
R = ____________
Lengths of Mg ribbon (cm)……... 3.56 | 3.62 Volume of H2 collected (mL)….….….…. 37.87 Height of water column (cm)….…..……..16.75 Temperature of water & gas (*C)….……..24.7 Mass of 250.0 cm of Mg (g)………….….. 1.876 Altitude of Denver (m)………………………. 1672 Reported bar. Pressure(inches Hg)….. 29.85
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7. Why magnesium? Give at least two reasons for this choice. 8. So why do meteorologists adjust all their reported barometric pressures to sea level? Hint, look at the map at right and consider how it would look if the pressures were not adjusted.
9. For each of the following potential error sources, write “H” if it would have made the R value come out too high, “L” if it would have made the R value come out too low, or “X” if it would not have had any effect at all.
__ Not all the Mg reacted; some of it got caught on the side of the tube.
__ A bubble of air got in when the tube was flipped over but no one noticed.
__ The magnesium wasn’t buffed enough before- hand.
__ Some of the hydrogen dissolved in the water as it bubbled up in the tube.
__ There were drops of water clinging to the inside of the tube above the water level.
__ There were bubbles of hydrogen clinging to the inside of the tube below the water level.
__ You accidentally recorded 33.27 mL as “33.72 mL.”
__ You forgot to change mL into L.
__ You forgot to subtract out the vapor pressure
__ 10. Consider the following measurement errors
A) being 1 cm off in the measuring of the water column height
B) being 1 cm off in the measuring of your Mg ribbon lengths
C) being 1*C off in the measuring of the temperature of the water/gas
D) being 1 mL off in the measuring of the volume of gas collected
E) being 1 inch off in the recording of the reported barometric pressure
Rank these five from greatest impact on your results (the
one that would throw off your experimental R value the most) to lowest impact. ___ ___ ___ ___ ___
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Graham’s Law of Diffusion Rates Tutorial Note sheet Name: ________________________
As you go through the power-point tutorial, every time you come across a (Q1) or (Q2), stop and answer that question on this sheet. Don’t worry about whether it’s right or wrong, just make your best guess. Then when you return to the tutorial and discover the correct answer, go back and fix your original answer, but do not erase. Just draw a line through what you had written (if it was wrong), and write the correct response after it. If your first response was correct, just go back and put a check mark (√) in front of it. For example:
QX: What is the capital of Connecticut? Connecticut City Hartford QY: How is element #9 spelled? √ fluorine
Q1: What do He and Ar have in common? ________________________________________________________________
Q2: What are some of the differences between He and Ar? _________________________________________________
Q3: Which balloon would be bigger? ____________________________________________________________________
Q4: Which gas would be at a higher temp? _______________________________________________________________
Q5: Which gas’s particles would have the greater average kinetic energy? ______________________________________
Q6: Which gas’s particles would have the greater velocity? __________________________________________________
Q7: How could a truck and a mini cooper travel down the highway with the same kinetic energy? __________________________________________________________
Q8: How much faster would a 1-ton mini cooper have to be moving to give it the same kinetic energy as a 10-ton truck? _________________________________________________ Q9: Solve for vHe : 4.003 amu · vHe
2 = 39.95 amu · (431 m/s)2 _______________ Q10: At a given temperature, carbon dioxide molecules travel at an average speed of 219 m/s. At that same
temperature, how fast would carbon monoxide molecules be moving? _______________
and how fast would fluorine molecules be moving? ________________
Q11: CH4 diffuses across the classroom at a rate of 48.9 cm/s. Under the same conditions, how fast would C3H8 diffuse? _______________ How about He? ________________ Q12: F2 diffuses through a small hole at the rate of 3.56 mL/sec. Under the same conditions, how fast would Xe effuse through that hole? _____________ How about H2? ___________
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Q13: At 77*C, oxygen molecules travel at an average speed of 522 m/s? At that same temp, Gas X particles travel at 558
m/s. What is the molecular weight of gas X? _____________What might it be? ____________
Q14: It takes one liter of Ne gas 15.2 sec to effuse through a small hole, and it takes 22.4 sec for a liter of gas Y to effuse
through that same hole. What is the molecular weight of gas Y? ___________What might it be? _____________
(Careful, those are times, not rates!)
Q15: Conceptual: Equal moles of A & B are in identical flasks at the same temperature. A has a greater molecular weight
than B. Which gas would have the higher
___ average kinetic energy of its particles?
___ average velocity of its particles?
___ average momentum of its particles (momentum = mv)
___ total force exerted on the inside of the flask by particle collisions
___ a higher collision rate with the inside walls of the flask
___ a higher force exerted per particle collision
___ more room for its particles to move around
___ rate of diffusion across the room if it leaked out of the flask?
___ time required to diffuse across the room
___ density
___ rate of speed for sound waves travelling through it???
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Graham’s Law WS Name: ____________________
1. What exactly is temperature a measurement of? _____________________________________________________
2. Why is it important to include the word “average” in your answer? _______________________________________
3. What two factors does an object’s kinetic energy depend on? ________________ _________________
4. What specifically is the physics equation for kinetic energy? ______________________
5. Which would increase the kinetic energy of an object more: doubling the object’s mass or doubling the object’s
velocity? ___________ Explain: __________________________________________________________________
6. State Graham’s Law as an equation for two gases, A and B, at the same temp: _______________________________
7. Consider two gases, He & O2, at the same temp. Which particles would have greater average kinetic energy? ______
Which particles are heavier? ______ Which particles would have greater average velocity? ______ Which gas would
diffuse across the room faster? ______
8. Two gas samples, one H2, one CO2, are such that their particles have the same average velocity. Which gas molecules
have the greater average kinetic energy? _______ Which gas is at the higher temperature? ______
Explain: ______________________________________________
For the remaining questions, use the Graham’s Law equation, show all work:
9. At a certain temperature, O2 molecules move with an average velocity of 345 mph. At that same temperature, what
would be the average velocity of a) He atoms? b) CO2 molecules?
a) _________ b) _________
10. A tank contains a mixture of three gases: N2, CH4 and HCN. a) Which gas’s particles have the greatest EK? b) Two
are the particle have velocities of 124.0 m/s and 126.3 m/s. What are the average velocities of all three gases?
a) ______ b) N2: _____ CH4: _____ HCN: ______
11. At a certain temperature, CH4 molecules move with an average velocity of 187 m/sec. At that same temp gas X
particles have an average velocity of 141 m/sec. a) Is gas X heavier or lighter than CH4? b) What is the molecular weight
(molar mass) of gas X? c) What is a possible identity of gas X?
a) _________ b) _________ c) _________
12. A tank contains a mixture of three gases: Ne, CO2 and gas Z. The three average velocities are 362 m/s, 389 m/s and
534 m/s. a) What are the average velocities of all three gases? b) What is the molecular weight and possible identity of
gas Z?
a) Ne: _____ CO2: _____ Z: ______ b) _____ ______
13. A sample of gas is at room temperature (22*C). To what temperature (*C) would it have to be taken to cause the
average velocity of the particles to double? _______ ...triple? _______ (Hint: Look back at you answers for #1 & #4).
Ans for 9-13 (IRO+3) 28.1 32.3 38.0 124.0 126.3 164.0 294 362 389 534 469 976 neither heavier fluorine nitrogen oxygen units: (m/s)x7 (mph)x2 (g/mol)x2 *C *C
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14. Explain the following three demos using words (no more than 40) and diagrams.
The He/air/SF6 voice demo: The He/air/SF6 balloon demo: The NH3/HCl tube demo:
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Dalton’s Law of Partial Pressures Note sheet Name: ________________________
As you go through the power-point tutorial, every time you come across a (Q1) or (Q2), stop and answer that question
on this sheet. Don’t worry about whether it’s right or wrong, just make your best guess. Then when you return to the
tutorial and discover the correct answer, go back and fix your original answer, but do not erase. Just draw a line through
what you had written (if it was wrong), and write the correct response after it. If your first response was correct, just go
back and put a check mark (√) in front of it. For example:
QX: What is the capital of Connecticut? Connecticut City Hartford QY: How is element #9 spelled? √ fluorine
Q1: What are the three main components of air and their percentages? ___________ ____________ ___________
Q2: What is the fourth most abundant component of air and its percentage? ____________
Q3: What do you think these percentages refer to? Percent by __________________
Q4: Why is this misleading? ___________________________________________________________________________
Q5: What do you think partial pressure means? ___________________________________________________________
Q6: What fraction of the total pressure is the Ar exerting? __________ … the He? ___________ … the Kr? ____________
Q7: What would the pressure be if He were the only gas present? ____________________________________________
Q8: What would the pressure be if Ar were the only gas present? _____________________________________________
Q9: How do mole fractions compare with particle fractions? _________________________________________________
Q10: Calculate the particle fraction (part/whole) and express it as a decimal: ____________________________________
Q11: Calculate the mole fraction (part/whole) and express it as a decimal: ______________________________________
Q12: Rather than count every egg, what could you do instead? _______________________________________________
Q13: Calculate XCO2 (the mole fraction for CO2) = ____________________ Q14: XNe = __________________________
Q15: What are the partial pressures of the CO2? _____________ and the Ne? _______________
Q16: What are two ways to determine PNe? ______________________________________________________________
Q17: A mixture contains He and O2 at a total pressure of 3.47 atm. The partial pressure of the He is 2.10 atm. What is
the partial pressure of the O2? ____________
Q 18: 1.92 moles of neon and 6.24 moles of chlorine are mixed together at a total pressure of 68.2 psi. What are their
mole fractions XNe: ___________ XCl2 __________ and partial pressures PNe: _____________ PCl2 _____________
Q19: 5.34 x 1021 CH4 cules and 1.68 x 1022 Xe atoms are mixed in a tank at a total pressure of 316 kPa. What are their
mole fractions XCH4: ___________ XXe __________ and partial pressures PCH4: _____________ PXe _____________
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Q20: 11.4 g of He, 25.6 g of Ar and 46.7 g of Kr are mixed together in a 20.00 L tank at a total pressure of 6.78 atm.
What are the partial pressures of the three gases? PHe: ___________ Par: ___________ PKr: __________ and what is
the temp (°C) of the mixture? ____________ [R = 62.4 L·torr/mol·K 0.0821 L·atm/mol·K 8.314 L·kPa/mol·K]
Q21: A canister contains 0.745 moles of oxygen and an unknown amount of fluorine all at a total pressure of 875 torr
and a temp of 28.3°C. Oxygen’s partial pressure is 687 torr. What is the fluorine’s mole fraction? ____________and
partial pressure, and what is the volume of the canister?
Q22: What mass of nitrogen gas must be added to a 30.0 L tank containing 25.0 g of Ne at 37.0°C to bring the total
pressure up to 225 kPa? ______________
Q23: A tank contains 3.86 g of CO and 5.77 g of Ne. The partial pressure of the CO is 437 torr. What is Ne’s mole
fraction? _____________ Ne’s partial pressure? ___________ and what is the total pressure in the tank? ___________
Q24: Conceptual: 2.5 moles of gas X and 1.5 moles of gas Y are mixed together in the same tank. Mark the following as
Always true, Sometimes true or Never True.
A) ___ X has a higher partial pressure than Y.
B) ___ X has a greater volume than Y.
C) ___ There is a greater mass of X present than Y.
D) ___ X is at a higher temperature (°C) than Y.
E) ___ X is at a higher temperature (K) than Y.
F) ___ X particles have a greater average kinetic energy than Y particles
G) ___ X particles are hitting the inside walls of the tank harder than Y particles.
H) ___ X particles are hitting the inside walls of the tank more often than Y particles.
I) ___ X particles are colliding with Y particles more often than Y particles are colliding with X.
J) ___ X particles are more concentrated in the tank than Y particles.
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Dalton’s Law of Partial Pressures WS Name: ____________________ 1. A flask contains Ne at 542 torr together with Ar at 234 torr. What will the total pressure be? Ans: ________ 2. A tank is filled with oxygen and nitrogen. The total pressure of the tank is 6.45 atm, and the partial pressure of the nitrogen is 2.07 atm. What is the partial pressure of the oxygen? Ans: ________ 3. a) A mixture contains 1.00 moles of CO2, 2.00 moles of He and 3.00 moles of CH4. Which gas has the highest partial pressure? _____ Which gas has the lowest partial pressure? ____
b) If the total pressure of the mixture above is 12.0 atm, what is the PCO2 ? ______ PHe ? ______ PCH4 ? ______
4. a) 1.25 moles of N2 and 6.41 moles of F2 are placed together in a 128 L tank at 755 torr. What is N2’s mole fraction in the mixture? What is the partial pressure of the N2? Ans: _______ ________ b) What is F2’s mole fraction, and what is the partial pressure of the F2? Ans: _______ ________ c)* What must the temperature (*C) of the mixture be? Ans: ________ 5. a) 3.23 g of Ne and 4.19 g of CH4 are placed together in a tank at 5.34 atm and 23*C. What is Ne’s mole fraction and what is the partial pressure of the Ne? Ans: _______ ________ b)* What must the volume of the tank be? Ans: ________ 6. A tank contains 5.86 g of Ar and 5.77 g of Ne. The partial pressure of the Ar is 237 torr. What is Ar’s mole fraction and what is the total pressure of the tank? Ans: _______ ________ 7. A flask contains 2.34 x 1022 atoms of He, 0.1972 moles of CO2 and 2.45 g of N2. The partial pressure of the N2 is 2.33 atm. What is N2’s mole fraction, and what is the total pressure of the mixture? Ans: _______ ________
(continued on the back)
Ans(IRO+1): -71 0.163 0.270
0.339 0.379 0.837 1.34 1.92
2.00 2.02 4.00 4.38 6.00
8.63 123 632 699 776
Units(IRO+1): atm atm atm
atm atm atm torr torr torr
torr CO2 CH4 L g *C
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8. Two gases A & B are placed together in a container. A’s partial pressure is greater than B’s. a) One reason one gas sample might have a higher pressure than another is because it is at a higher temperature. Why could this not be used to explain why A has a higher pressure than B? b) One reason one gas sample might have a higher pressure than another is because it is confined to a smaller volume. Why could this not be used to explain why A has a higher pressure than B? c) So, if it’s not temperature or volume, what explanation can you offer for why A has a higher pressure than B? d) Again, regarding the sample described above, label the following as DT definitely true, PT possibly true or DF definitely false: (Hint: there are 4 DT’s, 3 PT’s and 3 DF’s) ___ There is a greater mass of A present (compared to B) in the mixture. ___ There is a greater number of moles of A (compared to B) in the mixture. ___ There is a greater number of particles of A (compared to B) in the mixture. ___ A is at a higher temperature than B in the mixture. ___ A-particles are hitting the B-particles more often than B-particles are hitting A-particles. ___ A-particles are hitting the inside walls more often on average than B-particles. ___ A-particles are more concentrated in the container than B-particles. ___ A-particles don’t have as much room to move around as B-particles. ___ A-particles are heavier on average than B-particles. ___ A-particles are moving faster on average than B-particles. 9. Equal masses of P gas and Q gas are present in a container, yet P has a greater partial pressure than Q. Is this possible? Explain. 10. Equal number of moles of X gas and Y gas are present in a container, yet X has a greater partial pressure than Y. Is this possible? Explain.
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Life in a Vacuum Lab A Thought Experiment Name: _________________ Partner: _________________ So just how important is our atmosphere? Imagine you have been relocated to planet V, a planet just like Earth, with the exact same gravitational pull, but with no atmosphere at all. Which of the following fifty items would still work on this planet, and which ones would not? (Don’t use the cop-out answer, and say none of them would work because we’d all be dead: imagine you and your friends all have pressurized space suits, with oxygen tanks, etc...) For those things that would work, would they work exactly the same, perhaps even better? For those things that would not work, can you think of possible modifications that could enable them to work? Around the house...
1. a suction cup
2. a magnet
3. a drinking straw
4. a siphon
5. a light stick
6. a flashlight
7. a vacuum cleaner
8. a broom
9. an aerosol spray can
10. an alarm clock
Heating it up...
11. a match
12. a candle
13. a blow dryer
14. an electric stove
15. a gas stove
16. pressure cooker
17. a microwave oven
18. a convection oven
19. smoke rings
20. a smoke detector
Outdoor fun...
21. a boomerang
22. a yo-yo
23. a frisbee
24. a kite
25. a swing
26. a pogo stick
27. a bow and arrow
28. the game of golf
29. the game of baseball
30. a flower garden
Getting around...
31. a bicycle (and tire pump)
32. a hang glider
33. a golf cart
34. a helicopter
35. a parachute
36. a hover craft
37. an automobile (and air bag)
38. a hot air balloon
39. the Goodyear blimp
40. the space shuttle
We’re talking major energy...
41. a shot gun
42. an emergency road flare
43. dynamite (and fuse)
44. lightning (and thunder)
45. a coal burning power plant
46. a nuclear power plant
47. a nuclear warhead
48. a shooting star
49. our sun
50. a beautiful sunset
At the end of the period, the teacher will choose 10 of
the 50 items above for you to write up more extensively
on the following page.
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Powers of Ten Video WS Name: ________________ If you wish to view the video again, here is a convenient link: http://www.youtube.com/watch?v=0fKBhvDjuy0
1. As the camera pulls away from the picnic scene, every ten seconds, it moves ten times farther away. Is this speed constant, accelerating or decelerating? Explain. 2. At one point, the video shows a line move “at the true speed of light.” Why does it appear to move so slowly? 3. The video then uses a line to mark the orbit of the Earth. Why do they make the line so much wider than the Earth is? 4. When you’re driving down the highway, mile markers and signs seem to fly by you, but the hills on the horizon hardly seem to move at all. If you were going fast enough, however, even those hills would appear to fly by. Relate this to something described in the video. 5. “Looking back... we note four southern constellations still much as they appear from the far side of the Earth...” Why southern? 6. If the camera were pivoted 180 degrees, how would the statement in #5 above read? 7. This question is a little tricky, but think about it and you can get it: At right is a rough sketch of the milky way Galaxy as seen in the video. Draw sketches showing how the galaxy would have looked if the video had started... ...6 hours later: ...12 hours later: ...24 hours later: 8. What is meant by the words: “the richness of our own neighborhood?” and why is this called “the exception?” 9. If you were suddenly transported to some completely random place in the universe, describe what you would most likely be seeing?
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10. As the camera pulls in toward the man’s hand, every ten seconds, it moves ten times closer. Is this speed constant, accelerating or decelerating? Explain. 11. Sketch a DNA strand: 12. The video focuses in on one part of the DNA molecule: “a commonplace group of three hydrogen atoms bonded by electrical forces to a carbon atom.” What is the specific name we learned for those “electrical forces?” _____________ _______________ And why are there only three hydrogen atoms bonded to the carbon, if carbon always has four bonding sites? 13. Write the electron configuration for carbon: ________________ In the configuration, circle the four electrons that are referred to as “making up the outer shell of the carbon.” 14. “As we draw toward the atom’s attracting center,” why do “we enter upon a vast inner space?” 15. The narrator says: “At last, the carbon nucleus-- so massive and so small…” This description is a bit misleading; why? What should the narrator have said? ______________________________________________________ 16. As the nucleus is approached, the narrator says “this carbon nucleus is made up of six protons and six neutrons...” Why does he emphasize the word “this?” And what topic have we discussed this year that relates to this this-ness!? ________________ What other composition might a carbon nucleus have? 17. Organize the following objects from smallest to largest. a) a DNA strand b) the Milky Way Galaxy c) a white blood cell d) the Earth e) the Virgo Cluster f) the Sun g) our Solar System h) a carbon atom i) Chicago j) the Universe k) an atomic nucleus l) a proton m) the United States n) a cell nucleus
___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ (smallest) (largest) 18. How many times larger is our biggest view of nature (the diameter of the known universe) compared to our smallest view of nature (the diameter of a single proton in the nucleus of a carbon atom, beneath the skin on the hand of the sleeping man at the picnic)? __________. Now, use this number to approximate how many protons it would take to fill the known universe: ___________ Hint: it’s not just the same number, but given the three-dimensional nature of the universe, the calculation is one you should be able to do in your head.
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Powers of Ten Video Script The picnic near the lakeside in Chicago is the start of a lazy afternoon early one October. We begin with a scene one meter wide which we view from just one meter away. Now every 10 seconds we will look from 10 times farther away and our field of view will be 10 times wider. This square is 10 meters wide, and in 10 seconds the next square will be 10 times as wide. Our picture will center on the picnickers even after they’ve been lost to sight. 100 meters wide, the distance a man can run in 10 seconds. Cars crowd the highway, powerboats lie at their docks – the colorful bleachers are Soldier’s Field. This square is a kilometer wide (1000 meters) the distance a racing car can travel in 10 seconds. We see the great city on the lakeshore... 104 meters (10 kilometers): the distance a supersonic airplane can travel in 10 seconds. We see first the rounded end of Lake Michigan, then the whole great lake. 105 meters, the distance an orbiting satellite covers in 10 seconds. Long parades of clouds: today’s weather in the Middle West. 106 meters (a one with six zeros), a million meters – soon the Earth will show as a solid sphere. We are able to see the whole Earth now just over a minute along the journey. The Earth diminishes into the distance, but those background stars are so much farther away that they do not yet appear to move. A line extends at the true speed of light: in one second it half crosses the tilted orbit of the moon. Now we mark a small part of the path in which the Earth moves about the sun –now the orbital paths of the neighbor planets -- Venus... and Mars... then Mercury. Entering our field of view is the glowing center of our solar system: the sun, followed by the massive outer planets, swinging wide in their big orbits. That odd orbit belongs to Pluto. A fringe of a myriad commits too faint to see completes the solar system. 1014 -- as the solar system shrinks to one bright point in the distance, our sun is plainly now only one among the stars. Looking back from here we note four southern constellations still much as they appear from the far side of the Earth. This square is 1016 meters -- one light year -- not yet out to the next star. Our last 10 second step took us 10 light years further, the next will be 100. Our perspective changes so much in each step now that even the background stars will appear to converge. At last we pass the bright star Arcturus and some stars of the dipper. Normal but quite unfamiliar stars and clouds of gas surround us as we traverse the Milky Way Galaxy. Giant steps carry us into the outskirts of the galaxy, and as we pull away we begin to see the great flat spiral facing us. The time and path we chose to leave Chicago has brought us out of the galaxy along a course nearly perpendicular to the disk. The two little satellite galaxies of our own are the Clouds of Magellan.
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1022 power -- a million light years -- Groups of galaxies bring a new level of structure to the scene: glowing points are no longer single stars but whole galaxies of stars seen as one. We pass the big Virgo cluster of galaxies among many others 100 million light years out. As we approach the limit of our vision, we pause to start back home. This lonely scene, the galaxies like dust, is what most of space looks like. This emptiness is normal; the richness of our own neighborhood is the exception. The trip back to the picnic on the lake front will be a sped up version, reducing the distance to the Earth’s surface by one power of ten every 2 seconds. In each 2 seconds we will appear to cover 90% of the remaining distance back to Earth. Notice the alternation between great inactivity and relative activity, a rhythm that will continue all the way into our next goal: a proton in the nucleus of a carbon atom, beneath the skin on the hand of the sleeping man at the picnic. 109 meters, 108 ...7 ...6 ...5 ...4 ...3 ...2 ...1 We are back at our starting point. We slow up at 1 meter (10 to the zero power). Now we reduce the distance to our final destination by 90% every 10 seconds: each step much smaller than the one before. At 10-2 -- one one-hundredth of a meter (1 centimeter), we approach the surface of the hand. In a few seconds we will be entering the skin, crossing layer after layer, from the outermost dead cells into a tiny blood vessel within. Skin layers vanish in turn an outer layer of cells -- fealty collagen... the capillary containing red blood cells... and a ruffly lymphocyte. We enter the white cell -- among its vital organelles, the porous wall of the cell nucleus appears. The nucleus within holds the heredity of the man in the coiled coils of DNA. As we close in, we come to the double helix itself. A molecule like a long twisted ladder whose rungs of paired bases spell out twice in an alphabet of four letters the words of the powerful genetic message. At the atomic scale, the interplay of form and motion becomes more visible. We focus on one commonplace group of three hydrogen atoms bonded by electrical forces to a carbon atom. Four electrons make up the outer shell of the carbon itself. They appear in quantum motion as a swarm of shimmering points. At 10-10 meters (1 Angstrom), we find ourselves right among those outer electrons. Now we come upon the two inner electrons held in a tighter swarm. As we draw toward the atom’s attracting center, we enter upon a vast inner space. At last, the carbon nucleus-- so massive and so small. This carbon nucleus is made up of six protons and six neutrons. We are in a domain of universal modules: there are protons and neutrons in every nucleus, electrons in every atom, atoms bonded into every molecule out to the farthest galaxy. As a single proton fills our scene, we reach the edge of present understanding. Are these some quarks of intense interaction? Our journey has taken us through 40 powers of ten. If now the field is one unit, then when we saw many clusters of galaxies together, it was 1040 or one and forty zeros. 70
Cartesian Diver Silent Lab 20 pts Name: ________________ Assigned lab station: _____ The following lab will be done individually (no partners) and in complete silence (no talking). Any talking will result in a loss of points ( 2 pts first offense, then 4 more points, then three strikes you’re out -- you’ll be asked to sit down, and you’ll need to come in and do the lab after school to avoid getting a zero.) This lab is mostly an exercise in following directions and figuring out things on your own. That’s why you’re doing the lab individually and with no help from one another. Background: This whole experiment is about a small toy called a “Cartesian diver.” This toy is designed to be placed in a plastic soda bottle filled with water, the cap screwed on and as the bottle is squeezed, the toy dives to the bottom of the bottle; when the squeeze is released, the toy floats back up to the top. Procedure (Answer the questions as you go): 1. When you are ready, go to your assigned lab station. You should find the following equipment there: -- one plastic soda bottle filled with water. (Add a little water if necessary to bring the level up to within 2 cm of the very top) -- one testing tank (a large, cut-off soda bottle filled about two-thirds with water.) -- three “divers” labeled 1, 2, 3. (a “diver” is a cut-off plastic pipet with a hex nut screwed on) -- one “diver” labeled “4,” half-filled with colored water and sealed. -- one long wire hook -- one permanent marker
2. If any of the numbers have rubbed off the pipets, bring them to the instructor to renumber: As you handle the divers, try not to touch the numbers, they rub off pretty easily.
3. Pick up diver #1. Do you think it will float or sink when placed in water? _________ Place the diver into the testing tank. Does it float or sink? _______ Both the plastic pipet and the hex nut are more dense than water, so why does the diver float? ________________________________________
4. Now place the diver in the soda bottle, and screw the cap on tightly. Squeeze the bottle, gradually harder and harder. While you are squeezing, watch carefully what is going on inside the diver.
What do you observe? ____________________________________ In the boxes at right draw close-up pictures before and after the squeeze to show what changes are going on inside the diver: (draw divers as large as they are shown above.) Were you able to squeeze the bottle hard enough to get the diver to sink to the bottom of the bottle? ______ If not, don’t worry about it (although you may want to start hitting the weight room once in a while!)
5. Unscrew the cap, and use the hook to fish the diver out of the bottle. Place the diver back in the testing tank.
6. Squeeze the diver to force out about 14-16 air bubbles, then release the squeeze to draw up about 1 mL of water into
the diver. Let go of the diver in the testing tank. Does the diver still float? ______ Does it float higher or lower in the
water compared to how it was in step #3? ___________ Why? ____________________________________________
7. Repeat step 4. What is different this time? _____________________________________________________
8. Repeat step 5. Then squeeze a little more air out of the diver and let a little more water back in. See if it floats or sinks: ____________
9. Adjust the density of the diver so it just barely floats. In other words, get just the right amount of air in the diver so that it floats with its top just barely above the water level in the tank as shown at right: [If you squeeze out too much air, and the diver sinks in the tank, then lift it out of the tank, squeeze out a drop or two of water, and then release the squeeze to draw some air back into the diver. If the diver still sinks, repeat this step until it floats again.]
10. When you have the diver just barely floating, place the diver in the bottle, screw the cap on and bring it up to show to the instructor (3 pts.) along with this sheet with the questions above completed (2 pts).
1 2
3
4
before: after:
1
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11. Take the bottle back to your station and fish out the diver, and place it back in the testing tank.
12. Place divers #2 and #3 into the testing tank, and adjust their densities so they each barely float. Then fine tune the densities of all three so that when the divers are placed in the bottle, capped screwed on and the bottle squeezed with just one hand, the divers will go down in order -- 1 sinking first, then 2, then 3. This is something you have to figure out how to do on your own. When you have this task completed, bring it up to show the instructor that you can get your divers to go down in order using just one hand to squeeze the bottle.(3 pts).
13. Obtain a quick quiz from the instructor, sit down at your desk, fill it out and hand it back in (8 pts).
14. Now that you (hopefully) understand how a Cartesian diver works, do you think a diver would still work (go up and down) if its opening were plugged up with glue like diver #4 ? (Y/N) ____ Explain how it could work...or why it wouldn’t work: 15. Now take all the other divers out of the bottle and empty the water back into the testing tank, and place the sealed diver (#4) inside the bottle. Screw on the cap and squeeze the bottle gradually harder and harder. While you’re squeezing watch carefully what is happening to the diver. What do you observe? ___________________________________ In the boxes at right draw close-up pictures before and after the squeeze to show what changes are going on inside the diver: (draw divers as large as they are shown above.) Explain how, even though the diver was sealed, it was still able to dive when the bottle was squeezed: 16. Clean up your area, leaving it just the way you found it. When you have finished, call the instructor over to check your clean-up (2pts) If there are more than 20 minutes left in the class, try one or more of the bonus activities. Bonus A (+2): Bottle A at the front table has a sunken diver in it. Try squeezing the bottle edgewise as shown at right. What happens? _________________________ Explain: Bonus B (+1): Bottle B has a diver floating in it, but bottle B is made of glass. Try squeezing this bottle very hard and see what happens. What does this tell you about glass? Bonus C (+2): Bottles with C’s on them have floating divers with hooks and sunken divers with handles. Try using the hook to pick up the sunken diver and bring him to the surface. Show this to the instructor to get the credit on this one. Bonus D (+2) Cartesian divers have been around for centuries -- long before they had plastic pipets and plastic soda bottles. So what might the diver and container have been made of? Draw a picture:
before: after:
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Cartesian Diver Lab Questions Name: _______________________ 1. Explain using words and diagrams precisely how the Cartesian diver works. Your explanation should include words like “pressure,” “air pocket,” “density,” “compressible,” “volume,” “mass,” etc. Why does squeezing the bottle make the diver sink? Why does releasing the squeeze make the diver float back up? 2. Your explanation above of how a diver works probably depends on the diver being open on the bottom. Yet in the lab and the movie, you saw a closed-bottom (sealed) diver. Describe how it behaves differently than a regular open-ended diver. Explain using words and diagrams why it still works. 3. How does the ability of the diver to dive depend on the fact that gases are compressible and that liquids are not? 4. If you wanted to make a series of divers, like in the movie, that spelled out a word like “H-E-L-L-O,” how would you do it? Use words and diagrams. 5. In the movie, you also saw a diver with glitter fountaining up inside. Explain, using words and diagrams how it was made. Was it an open diver or a closed one? 6. In the movie, you also saw a Jaws diver whose mouth opened up when it dived. Explain, using words and diagrams how it was made. Was it an open diver or a closed one?
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7. In the movie, you also saw a Rudolf the red nose diver whose nose lit up when it dived. Explain, using words and diagrams how it was made. Was it an open diver or a closed one? 8. You also saw a wadded-up piece of aluminum foil work as a diver. Explain how that would work. 9. A nail is pushed into a piece of styrofoam packing material. Do you think that would work as a diver? Explain. 10. A candle (which floats) is tied to a paper clip. Do you think that would work as a diver? Explain. 11. What, if anything, would you have had to do differently in the diver lab if you had used... a) ...oil instead of water? b) ...a heavier hex nut? c) ...a small pipet? d) ...a larger bottle? e) ...helium instead of air? 12. A Cartesian diver is stuck on the bottom, with not quite enough air to get it to the top. List five different ways to get the sunken diver to the top of the bottle, and explain why you think each would work. (Hint: Think of the different factors you’ve learned about that affect a gas’s volume.) 1)
2)
3)
4)
5)
13. Sometimes, if a diver is set to be very sensitive, so it is just barely less dense than water, it will sink just fine, but then when the squeeze is released, it does not float back up, even though no air has been lost out of it. Explain why that happens.
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Eudiometer Lab (15 pts) Name: _____________ Partner: _____________
A eudiometer is a device used to measure changes in gas volumes during a chemical reaction. Watch the video of a eudiometer in action. Then in the space at right explain how one works, including before and after diagrams. Make sure to explain what happens to the product.
Now consider the four substances: below, jot down everything you can about each of them in terms of how reactive they are or what they are made up of – perhaps demos or labs we have done this year that featured them.
H2 (hydrogen)
O2 (oxygen)
He (helium)
Air
Now in this lab, you will be given 4 syringes: one contains oxygen, one contains hydrogen, one contains helium, and one
contains ordinary air. If you know your chemistry, you should realize that of the six possible pairings, only two
combinations will react – one much more vigorously than the other. Answer questions A through D below.
A: Which two gases would react most vigorously? ___ ___
B: Write a balanced equation for this reaction: ________________________
C: And which combination would react, but not as vigorously? ___ ___
D: Why will it be less vigorous? _________________________________________________________
Task #1 (10 pts): Figure out which gas is which. Advice: Use the
gases sparingly. Once the syringes are empty, that’s it: no refills
(unless you come in after school!) H2 = ______ O2 = ______ He = ______ air = ______
Task #2 (3 pts): Place some mixture of gases in the eudiometer with a total volume of between 6 mL and 8 mL, and have
the volume after the reaction be precisely 4.0 mL. (Rounds to 4 mL = full credit, right on 4.0 mL = +1 bonus!)
Task #3 (2 pts): Place some mixture of gases in the eudiometer with a total volume of between 6 mL and 8 mL, and have
the volume after the reaction be precisely 1 mL. (Rounds to 1 mL = full credit, right on 1.0 mL = +1 bonus!)
Task #4 (BONUS 5 pts): Collect data from the eudiometer that will enable you to determine the percent oxygen in air.
You will want to use about 6-7 mL of air and about 6-7 mL of hydrogen. Show your data and calculations below.
As soon as you can, bring the cup containing the four syringes up to the instructor, and get a new set to take back to
your lab bench for the next period.
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Before: After:
Explanation:
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