Name ____________________________________________ Period. _________
Chem RG Chapter Packet 12 Gases
Assign Section # Name 10 5
1. Assignment Sheet printed
2. Notes 12.1 (plus add Evidence, see below)
3. Notes 12.2 (plus add Evidence, see below)
4. Notes 12.3 (plus add Evidence, see below)
5. Worksheet 12.1
6. Worksheet 12.2
7. Worksheet 12.3
TD Worksheet– Gas Laws Activity (turn in separately for graded points
Ch 12 Test Review (turn in separately for graded points)
Lab A9 (turn in separately for graded points)
(Total Points = 7 x 10 = 70)
Notes: 1. Your lab report is turned in by itself and receives a separate grade. 2. Your test reviews are graded separately. 3. Website: http://chem-rg-flipped.santiago.groupfusion.net/
EVIDENCE (after you take notes.) You should have at least 4 types of evidence for each set of notes. 1. Number new concepts 1,2,3…/A,B,C… 2. Delete/Cross out unimportant information Unimportant
3. Circle vocab/key terms 4. Identify points of confusion ?
5. Underline/Highlight main Ideas Main Ideas 6. Identify information to be used on a test, essay… *
7. Fill in gaps of information. Reword or paraphrase. ^ 8. Create visuals/symbols of important
information Visuals/symbols
Key Terms
Chem RG Experiment A9 – Molar Volume of a Gas
Objectives • Determine the volume of hydrogen produced by the reaction of a known mass of
magnesium with hydrochloric acid. • Compute the volume of the gas at standard temperature and pressure. • Relate the volume of gas to the moles of magnesium reacted. • Infer the volume of one mole of gas at standard temperature and pressure.
Introduction Magnesium is an active metal that readily reacts with hydrochloric acid to produce hydrogen gas. In this experiment, you will react a known amount of magnesium with hydrochloric acid and collect and measure the volume of hydrogen gas produced. From the volume of the gas measured at atmospheric pressure and the temperature of the lab, you can calculate the volume of the gas at standard temperature and pressure. Knowing the mass of magnesium, you can calculate the moles of magnesium consumed and determine the volume of hydrogen at STP produced by the reaction of one mole of magnesium. This conclusion can then be related to the balanced equation for the reaction. Materials • 6 M HCl • 50 mL beaker • 50 mL eudiometer • 400 mL beaker • thread
• buret clamp • magnesium ribbon (untarnished) • ring stand • rubber stopper, one-hole, #00 • thermometer, nonmercury, 0–100°
Procedure 1. Copy Figures A & B (below) into your lab book and refer to them when doing steps 5 and 9. 2. Fill a 400 mL beaker two-thirds full of water that has been adjusted to room temperature.
Record the temperature of the water and put into your data table. 3. Measure a length of magnesium ribbon to the nearest 0.1 cm. Your piece of magnesium
should not exceed 3.5 cm. Record the length of the ribbon in the Data Table. 4. The mass of Mg is 1.078 g/meter. Record this in your data table. 5. Coil your magnesium ribbon around a pencil into a loose coil. Then remove & tie it as in
Figure A with one end of a piece of thread approximately 25 cm in length. All the loops of the coil should be tied together as shown in Figure A.
6. CAUTION Hydrochloric acid is caustic and corrosive. Avoid contact with skin and eyes. Carefully pour approximately 10 mL of 6 M HCl into a 50 mL beaker and then pour the 10 mL of HCl into your gas measuring tube or eudiometer.
7. While holding the eudiometer in a slightly tipped position, very slowly pour water from the 400 mL beaker into the eudiometer, being careful to layer the water over the acid so that they do not mix. Add enough water to fill the eudiometer to the brim.
8. Lower the magnesium coil into the water in the eudiometer tube to a depth of about 5 cm. Insert the rubber stopper into the open end of the eudiometer to hold the thread in place, as
shown in Figure A on the previous page. The one-hole stopper should displace some water from the tube. This ensures that no air is left inside the tube. MAKE SURE YOUR STOPPER ONLY HAS ONE HOLE.
9. Cover the hole of the stopper with your finger, and invert the eudiometer into the 400 mL beaker of water. Clamp the eudiometer tube into position on the ring stand, as shown in Figure B. Answers the next 2 questions and describe your observations in the place provided following the Data Table
a. Why does the acid flow down the tube to react with the magnesium? (Hint: think about density)
b. Is the acid now more concentrated or dilute after it has flowed down the tube? Why? 10. When the magnesium has disappeared entirely and the reaction has stopped, read the volume
of hydrogen you collected as accurately as possible. 11. Record the temperature of the room and the atmospheric pressure (look at the barometer in
our room, which also has a thermometer. Also, the barometer reads in cm, but you need to report it in mm).
12. Use the table of water-vapor pressures on p. 835 your textbook to find the vapor pressure of water at the temperature of the room. Record this water-vapor pressure in your data table.
13. Clean your lab station AND refill the 400-mL beakers with tap water so that they will come to room temperature and be ready for the next period.
DATA TABLE Length of Mg used cm Mass per meter of Mg (see step 4) g/m Volume of H2 collected under lab conditions mL Temperature of H2 collected °C Barometer reading mm/Hg Vapor pressure of water at observed temperature °C
OBSERVATIONS – write your Step 9 observations below your data table. CALCULATIONS 1. Organizing Data From the length of the magnesium ribbon you used and the mass of a
meter of magnesium ribbon, Determine the mass of the magnesium that reacted. Record this result and all your calculated results in your calculations table. Be sure you make a calculations table!
2. Organizing Data Calculate the number of moles of magnesium that reacted. Hint: use bar = bar with your answer in Calculation 1 above.
3. Organizing Data Because the H2 gas was collected over water, two gases were present in the eudiometer: hydrogen and water vapor. Calculate the partial pressure of the hydrogen gas you collected. (Hint: The sum of the two partial pressures equals atmospheric pressure. Find water's partial pressure at your measured temperature from the table in your book. Use this plus the atmospheric pressure from the barometer to calculate hydrogen's partial pressure.)
4. Organizing Data Calculate the volume of the dry hydrogen you collected at the measured temperature and standard pressure. (Hint: P1V1 = P2V2 ). Use the volume you measured as V1, the pressure from Calculation #3 as P1 and standard pressure in mm Hg (you should know this) as P2, and then solve for V2.
5. Organizing Data Calculate the volume of the dry hydrogen gas at standard temperature. Use Calculation #4 as V1, the temp you measured (in K) as T1, standard temp for T2 & solve for a revised V2.
6. Inferring Conclusions Calculate the volume of dry hydrogen gas that would be produced by one mole of magnesium at standard temperature and pressure. Hint: Calculation #5 answer ÷ Calculation #2 answer. See how close your answer is to 22,400 mL = 22.4 L (standard molar volume).
7. Calculation Table Be sure to make one! Put it in your final report. GENERAL CONCLUSIONS 1. Relating Ideas Write a balanced equation for the reaction of magnesium with HCl. The
products are hydrogen gas and MgCl2. 2. Applying Conclusions From the balanced equation above, determine the volume of
hydrogen gas at STP that can be produced from three moles of magnesium reacting with hydrochloric acid.
HC Chapter 12 Gases
12.1 Characteristics of Gases
• Describe the general properties of gases. • Define pressure and its units. • Convert between units of pressure. • Relate the kinetic-molecular theory to the properties of an ideal gas.
Pressure Pressure is the result of __________ of the molecules with the sides of a container (test question)
A vacuum has __ pressure. Pressure i measured in atmospheres (atm) or mm Hg or Torr or kilopascals.
It is measured with a __________. Barometer - measures atmospheric pressure.
Barometer 101,325 Pa = 101.325 kPa = 1 atm = 760 mm Hg = 760 Torr.
Be able to __________ between these!
Types of Pressure Units Pressure Used in 760 mm Hg or 760 torr Chemistry 14.7 lb/in.2 U.S. pressure gauges 29.9 in. Hg U.S. weather reports 101.3 kPa (kilopascals) Weather in all countries except U.S. 1.013 bars Physics and astronomy 1.00 atm = 760 mm Hg = 760 torr = 14.7 psi pp A. What is 475 mm Hg expressed in atm? 475 mm Hg x 1 atm = 0.625 atm
760 mm Hg B. Tire pressure = 29.4 psi. Convert to mm Hg. YOU TRY THIS ONE BELOW: Units of pressure (see Sample Problem A, p. 420) 1 atmosphere = 760 mm Hg. 1 mm Hg = 1 torr. 1 atm = 101,325 Pascals = 101.325 kPa What is 724 mm Hg in Pa? Solution and answer: (724/760)(101,325) = 96,500 Pa in torr? YOU TRY BELOW in atm? YOU TRY BELOW
Section 12.2 The Gas Laws
• Use the kinetic-molecular theory to explain the relationship between gas volume, temperature & pressure. • Use Boyle’s law to calculate volume-pressure changes at constant temp. • Use Charles’ law to calculate volume-temperature changes at constant press. • Use Gay-Lussac’s law to calculate pressure-temperature changes at constant volume. • Use the combined gas law to calculate volume-temperature-pressure changes.
Boyle’s Law At a constant temperature, pressure and volume are __________ related.. As one goes up the other goes down. P1 x V1 = P2 x V2 Use this for __________ Freon-12, CCl2F2, was used in refrigeration systems. What is the new volume (L) of a 1.6 L sample of Freon gas initially at 50 mm Hg after its pressure is changed to 200 mm Hg at constant T? Prepare a data table DATA TABLE Initial conditions Final conditions P1 = 50 mm Hg P2 = 200 mm Hg V1 = 1.6 L V2 = ? Find New Volume (V2) using P1V1 = P2V2 Solve for V2: V2 = P1V1
P2 V2 = 1.6 L x 50 mm Hg = 0.4 L
200 mm Hg
Charles’ Law The volume and absolute temperature (K) of a gas are __________ related at constant mass & pressure
Temperature __________ be in __________ If you start with 1 liter of gas at 1 atm pressure and 300 K and heat it to 600 K one of 2 things happens: Either the volume will increase to 2 liters at 1 atm if pressure stays the same; Or the pressure will increase to 2 atm if volume is fixed. (Or someplace in between) V1/T1= V2/T2 Use this for Charles’ Law calculations V and T Problem: A balloon has a volume of 785 mL on an autumn day when the temperature is 21°C. In the winter, the gas cools to 0°C. What is the new volume of the balloon? Complete the following setup: Initial conditions Final conditions
V1 = 785 mL V2 = ? T1 = 21°C = 294 K T2 = 0°C = 273 K
Since V1/T1= V2/T2, V2 = V1T2/T1 V2 = (785 ml)(273 K)/294 K
Answer = 729 mL Check your answer: If temperature decreases, V should decrease. What is the temperature of a gas that is expanded from 2.5 L at 25ºC to 4.1 L at constant pressure. V1/T1= V2/T2 SHOW YOUR WORK BELOW, CIRCLE YOUR ANSWER
Gay-Lussac’s Law The __________ and absolute __________ (K) of a gas are directly related at constant mass & volume P1/T1= P2/T2 use this formula What is the pressure inside a 0.250 L can of deodorant that starts at 25ºC and 1.2 atm if the temperature is raised to 100ºC? Note: Volume is constant (0.250 L) P1/T1= P2/T2 (1.2 L)/(298 K) = (P2)/(373 K), answer = 1.5 atm.
Combined Gas Law (P1 x V1)/T1= (P2 x V2)/T2 Example: Solve the combined gas law for T2 (Hint: cross-multiply the “combined” first.) P1V1 = P2V2 T1 T2
P1V1T2 = P2V2T1 So, T2 = P2V2T1 P1V1
SHOW YOUR WORK BELOW: A 15 L cylinder of gas at 4.8 atm at 25ºC is heated to 75ºC and compressed to 17 atm. What is the new volume? (ans. 4.9 L)
True or False
1.___The P exerted by a gas at constant V is not affected by the T of the gas.
2.___ At constant P, the V of a gas is directly proportional to the absolute T
3.___ At constant T, doubling the P causes the V of gas sample to decrease to one-half its original V.
The Fourth Part: Volume and Moles Avogadro's Hypothesis: V is __________ proportional to number of molecules at constant T and P. V1/n1 = V2/n2
Equal __________ of gas at the __________ temperature and pressure have equal numbers of __________.
Standard Temperature and Pressure 0ºC and 1 atm pressure. Abbreviated as __________ At STP 1 mole of gas occupies 22.4 L. Called the __________ __________
The effect of adding gas. When we blow up a balloon we are adding gas molecules.
Doubling the number of gas __________ doubles the __________ (at same volume at the same temperature).
Pressure and the number of molecules are __________ related
More molecules means __________ collisions. Fewer molecules means __________ collisions.
Gases naturally move from areas of high pressure to low pressure because there is empty space to move in.
If you __________ the number of molecules, you __________ the pressure. What is the volume of 4.59 moles of CO2 gas at STP? 103 liters. (4.59 mol)(22.4 L /mol) How many moles is 5.67 L of O2 at STP? (5.67 L)(1 mol/22.4 L) = 0.253 moles O2 What is the volume of 8.8 g of CH4 gas at STP? (Watch significant figures) SHOW WORK. Ans. 12 L
12.3 Molecular Composition of Gases • Solve problems using the ideal gas law. • Understand Graham’s law of diffusion • Understand Dalton’s law of partial pressure.
Ideal Gases In this chapter we are going to assume the gases behave ideally. Does not really exist but makes the math easier and is a close approximation.
We assume that particles have no __________. We assume there are __________ __________ forces. PV = nRT. R can be 0.0821 l•atm/mol•K = 8.314 l•kPa/mol•K = 62.4 l•mmHg/mol•K
WATCH UNITS (atm or kPa or mmHg) Dinitrogen monoxide (N2O), laughing gas, is used by dentists as an anesthetic. If 2.86 mol of gas occupies a 20.0 L tank at 23°C, what is the pressure (mmHg) in the tank in the dentist office? Steps . . . Set up data for 3 of the 4 gas variables . Adjust to match the units of R (hint: want pressure in mmHg) V = 20.0 L 20.0 L T = 23°C + 273 296 K n = 2.86 mol 2.86 mol P = ? ? Rearrange ideal gas law (PV = nRT) for the unknown P P = nRT
V Substitute values of n, R, T and V and solve for P P = (2.86 mol)(62.4L-mmHg)(296 K) (20.0 L) (K-mol) = 2.64 x 103 mm Hg Find moles of air in a 2.0 L bottle at 19ºC & 747 mm Hg? Hint: solve for “n”. SHOW WORK. Ans. 0.082 mol PV = nRT, so n = PV/RT. Set up . . What is the pressure in atmospheres exerted by 1.80 g of H2 gas in a 4.30 L balloon at 27ºC? Hint: convert g to mol (use molar mass) then use PV = nRT & solve for P.. SHOW WORK. Ans. 5.10 atm Answer is . . .
Using the Combined vs the Ideal Gas Law pp PV = nRT tells how a gas is NOW (no change in pressure, temperature or volume). Use combined gas law P1 V1 = P2 V2
T1 T2 when one of the variables changes.
Gas Stoichiometry What volume of CO2 forms from 5.25 g of CaCO3 at 103 kPa & 25ºC? 1. First write the equation: CaCO3 CaO + CO2 2. Use “bar = bar” to convert 5.25 g CaCO3 to mol of CaCO3 (ans. 0.0525 mol) 3. Use mole ratio to find mol of CO2 (ans. 0.525 mol since 1:1 ratio) 4. Plug into PV = nRT to find volume (ans. 1.26 L)
Graham’s Law Diffusion - Spreading of gas molecules __________ a __________ until __________ distributed. Effusion - Passing of gas molecules through a __________ opening in a container Bigger molecules move __________at the same temp. (test question!) Helium effuses and diffuses __________ than air - so it escapes from balloon into the air. Rate of effusion of a gas is __________ related to the ________ ________ of its ________ ________. Ratea = √Mb
Rateb √Ma
A molecule of oxygen gas has an average speed of 12.3 m/s at a given temp and pressure. What is the average speed of hydrogen molecules at the same conditions? COPY FROM THE SLIDE
Dalton’s Law The _____ pressure of a ________ of gases equals the _____ of the ______ pressures of the individual gases. What is the total pressure in a balloon filled with air (O2 & N2) if the pressure of the oxygen is 170 mm Hg and the pressure of nitrogen is 620 mm Hg? Answer: 790 mm Hg. (170 mm Hg + 620 mm Hg) Gases Collected by Water Displacement A gas collected by water displacement is not pure, but mixed with water vapor. This is a very common way to collect a gas experimentally. We use Dalton’s Law of Partial Pressures to find the pressure of the pure gas. A gas collected by water displacement is not pure, but mixed with water vapor. Patm = Pgas + Pwater vapor So, to get the pressure of the pure gas we must subtract the water vapor pressure. Pgas = Patm - Pwater vapor We can look up the PH2O at a specified temperature (see next slide). You’ll use this in Lab A-9 Gas Collection Example What is the pressure of N2 gas is collected over H2O at 23.0ºC with atmospheric pressure of 785 Torr. . . Patm = Pgas + Pwater vapor Pwater vapor at 23.0 ºC = 21.1 Torr 785 Torr = PN2 + 21.1 Torr, so PN2 = ? . . 764 Torr (remember sig figs)
Chem RG Chapter 12 worksheet. Dr. Lachman. SHOW YOUR WORK! 12.1 Book Reference: See sample problem “A” p. 420 to learn how to do the problems below, which are p. 420 #1-4 and p. 422 #8-10. Try to get these answers: p. 420: 1) 7.37 x 106 Pa. 2) 92.48 mm Hg. 3) 0.9869 atm. 4) 3.08 × 105 Pa Now, do p. 422: 8) 0.57 atm. 9) 610.5 Pa. 10) 1.3 x 10-3 Pa.
12.2 worksheet (2 pages). See sample problem “B” p. 425 to do p. 425: 1-4 3 Ans. 1) 142 mL. 2) 6.58 mL. 3) 8.1× 105 L. 4) 1.38 × 102 mL See sample problem “C” p. 428 to do p. 428: 1-4 Ans. 1) 0.67 L 2) 815 mL 3) -11.0 ºC 4) 1.64 × 103 L
(Continue to next page for the rest of 12.2 Worksheet)
See sample problem “D” p. 430 to do p. 431: 1-3 (skip #4) Ans. 1) 1.29 atm 2) 325 K or 52 C 3) 491 K or 218 C
12.3 worksheet (2 pages). See sample problem “E” p. 435 to do p. 435: 1-4 Ans. 1) 7.97 × 10-2 mol 2) 0.137 mol .
3) 1500 kPa. 4) 2.73 × 104 L See sample problem “F” p. 438 to do p. 438: 1-2 (skip 3 & 4) Ans. 1) You do on your own. 2) 1.9 × 103 m/s
(Continue to next page for the rest of 12.3 Worksheet)
See sample problem “G” p. 441 to do p. 442: 1-3 Ans. 1) 11.4 L 2) 2.08 × 105 L H2O ) 3.87 g Na
Chapter 12 Test Review ( 2 pages): Show your work below. See pp. 446-447 #s 32, 35, 45, 49, 52, 58, 60. 32. The vapor pressure of hydrogen peroxide is 100.0 torr at 97.0 ºC. What is this pressure in kPa? Ans. 13.3 kPa 25. A gas has a volume of 125 mL at 91.0 kPa. What is its volume at 101 kPa? Ans. 113 mL 45. A person breathes 2.6 L of air at -11 ºC into her lungs where it is warmed to 37 ºC. What is its new volume? Ans. 3.1 L. 49. A sample of helium has a pressure of 101 kPa at 25ºC. What will it be at 77 ºC assuming constant valume? Ans. 119 kPa. 52. How many moles of argon are in 20.0L at 25 ºC and 96.8 kPa? Ans. 0.781 mol. 58. An unknown gas effuses at half the speed of oxygen. What is its molar mass? Is it HBr or HI? Ans. 128 g/mol, then you need to decide if it is HBr or HI. 60. How many liters of hydrogen gas can be produced at 300.0 K and 103 kPa if 20.0 G of sodium metal is reacted with water as follows: 2Na + 2H2O 2NaOH + H2? Ans. 10.4 L
The most common units that are used for Pressure are __________, __________, __________, & __________. STP stands for ______________________________________________ and the values are _________ & _________ When performing ANY gas law equation, YOU MUST convert _____________ to _____________ or your answer will be wrong!!!! What are the four main concepts of the KMT? (Hint: See p. 421 in your book)
1) _________________________________________________________________________________________________ 2) _________________________________________________________________________________________________
3) _________________________________________________________________________________________________ 4) _________________________________________________________________________________________________
Put the following in order from lowest to highest density: CO2 (l), CO2 (s), CO2 (g) : _____________________________ What is compression and how does it affect gases? __________________________________________________________________ ________________________________________________________________________________________________________ What is diffusion and how does it affect gases? _____________________________________________________________________ ________________________________________________________________________________________________________ Give the equation for the following Gas Laws: Charles’ Law _________________________ Boyles’ Law ______________________________ Gay Lussacs’ Law _________________________ Combined Gas Law _________________________ Explain Avogadro’s Law ________________________________________________________________________________________ According to _____________ Law, __________ L = __________ mol, therefore 0.0500 L = ___________ mol
45 mol = ___________ L
Who related pressure & volume? ____________, pressure & temperature? ____________, volume & temperature? ____________ Draw a brief graph of the relationship between the given variables (remember to label your variables):
Pressure vs Volume
Temperature vs Volume
Temperature vs Pressure
Name: ____________________________________________________ Date: __________ Period: _______ Go to: http://www.pbslearningmedia.org/shared/blachman/chemsharks/ Go to page 2 and do "Gas Properties" 1) Make the Volume constant. Pump the handle 3 times. Increase the temperature to around 700 K. What happened to the pressure when you increased the temperature? PBS Learning Gas Properties ______________________________________________________________________________________ What happened to the gas particles when you increased the temperature? ______________________________________________________________________________________ Decrease the temperature to around 50 K. What happened to the pressure when you decreased the temperature? ______________________________________________________________________________________ What happened to the gas particles when you decreased the temperature? ______________________________________________________________________________________ What is the name and formula of the Gas Law that you are demonstrating here? __________________________ What is the relationship between Temperature and Pressure? _______________________________________ _______________________________________________________________________________ 2) Press the Reset button Make the Pressure constant. Pump the handle 3 times. Increase the temperature to around 700 K. What happened to the volume when you increased the temperature? ______________________________________________________________________________________ What happened to the gas particles when you increased the temperature? ______________________________________________________________________________________ Decrease the temperature to around 50 K. What happened to the volume when you decreased the temperature? ______________________________________________________________________________________ What happened to the gas particles when you decreased the temperature? ______________________________________________________________________________________ Now, try to increase the volume, what happens?__________________________________________________ What is the name and formula of the Gas Law that you are demonstrating here? __________________________ What is the relationship between Temperature and Volume? ________________________________________ _______________________________________________________________________________ 3) Press the Reset button Make the Temperature constant. Pump the handle 3 times. Go on to next page
Increase the Volume. What happened to the pressure when you increased the volume? ______________________________________________________________________________________ What happened to the gas particles when you increased the volume? ______________________________________________________________________________________ Decrease the volume. What happened to the pressure when you decreased the volume? ______________________________________________________________________________________ What happened to the gas particles when you decreased the volume? ______________________________________________________________________________________ Now, pump the handle 4 times, what happens?____________________________________________________ What is the name and formula of the Gas Law that you are demonstrating here? __________________________ What is the relationship between Pressure and Volume? ____________________________________________ _______________________________________________________________________________ 4) Press the Reset button Set the constant to none. Pump the handle 3 times. Decrease the Volume. What happened to the pressure and temperature when you decreased the volume? ______________________________________________________________________________________ What happened to the gas particles when you decreased the volume? ______________________________________________________________________________________ Decrease the temperature to around 50 K. What happened to the volume and pressure when you decreased the temperature? ______________________________________________________________________________________ What happened to the gas particles when you decreased the temperature? ______________________________________________________________________________________ Increase the Volume. What happened to the pressure and temperature when you increased the volume? ______________________________________________________________________________________ What happened to the gas particles when you increased the volume? ______________________________________________________________________________________ Decrease the Volume again. What happened to the pressure and temperature when you decreased the volume? ______________________________________________________________________________________ What happened to the gas particles when you decreased the volume? ______________________________________________________________________________________ Now, pump the handle 3 times, what happens?____________________________________________________ Next, Slide the top over to release some of the particles, what happens? _______________________________ ______________________________________________________________________________________ What variable are you adjusting by pumping the handle and/or moving the top to release some particles? ________ What is the name and formula of the Gas Law that you are demonstrating here? __________________________