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DESCRIPTION
TRANSCRIPT
Chapter 1Chemistry and Measurement
?
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Example of The law of conservation of mass: Aluminum powder burns in oxygen to produce a substance called aluminum oxide. A sample of 2.00 grams of aluminum is burned in oxygen and produces 3.78 grams of aluminum oxide. How many grams of oxygen were used in this reaction?
aluminum + oxygen = aluminum oxide
2.00 g + oxygen = 3.78 g
oxygen = 1.78 g
?
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Potassium is a soft, silvery-colored metal that melts at 64°C. It reacts vigorously with water, with oxygen, and with chlorine. Identify all of the physical properties and chemical properties given in this description.
Reacts with chlorineMelting point (64°C)
Reacts with oxygenSilvery-colored
Reacts with waterSoft
Chemical PropertyPhysical Property
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?
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Perform the following calculation and round your answer to the correct number of significant figures:
Calculator answer:
3.23225000
The answer should be rounded to two significant figures (92.35 X 0.035):
3.2
)421.0456.0(35.92
?
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In winter, the average low temperature in interior Alaska is -30.°F (two significant figures). What is this temperature in degrees Celsius and in kelvins?
F9
C5F32
ο
οο
FC tt
F9
C5F62
ο
οο
C t
F9
C5F32F.30
ο
οοο
C t
C34.4444444οC t
C34οC t
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K15.273C1
K1οCK
tt
K15.273C1
K1C34
οο
K
t
K15.273K34K t
K15.239K t
K239K t
?
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Oil of wintergreen is a colorless liquid used as a flavoring. A 28.1 g sample of oil of wintergreen has a volume of 23.7 mL. What is the density of oil of wintergreen?
V
md
mL23.7
g28.1
V
m
mL23.7
g28.1d
mL
g1.18565491d
mL
g1.19d
?
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The dimensions of Noah’s ark were reported as 3.0 × 102 cubits by 5.0 × 101 cubits. Express this size in units of feet and meters. (1 cubit = 1.5 ft)
(exact)m0.9144yd1
yd1ft3
ft1.5cubit1
cubit1
ft1.5cubits103.0 2
ft104.5000000 2byft104.5 2
cubit1
ft1.5cubits105.0 1
ft107.5000000 1ft75ft107.5 1
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(exact)m0.9144yd1
yd1ft3
ft1.5cubit1
m101.37160000 2
yd1
m0.9144
ft3
yd1ft104.5 2
bym101.4 2 m23
yd1
m0.9144
ft3
yd1ft75
m22.8600000
byft104.5 2 ft75ft107.5 1
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Chapter 2Atoms,
Molecules, and Ions
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Write the nuclide symbol for the atom that has 19 protons and 20 neutrons.
K3919
Atomic number: Z = 19The element is potassium, K.
Mass number: A = 19 + 20 = 39
The nuclide symbol is
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An element has four naturally occurring isotopes. The mass and percentage of each isotope are as follows:
Percentage Abundance Mass (amu)
1.48 203.973
23.6 205.9745
22.6 206.9759
52.3 207.9766
What is the atomic weight and name of the element?
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To find the portion of the atomic weight due to each isotope, multiply the fraction by the mass of
the isotope. The atomic weight is the sum of these products.
Fractional Abundance
Mass (amu) Mass From Isotope
0.0148 203.973 3.01880040
0.236 205.9745 48.6099820
0.226 206.9759 46.7765534
0.523 207.9766 108.771762
207.177098The atomic weight is 207 amu; the element is lead.
Total =
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What is formula of the ionic compound of Mg2+ and N3-?
The common multiple of the charges is 6, so we need three Mg2+ and two N3-. The resulting formula is
Mg3N2
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Common Monatomic Ions of the Main-Group Elements
Bi3+Pb2+Tl3+, Tl+
Ba2+Cs+
I-Te2-Sn2+In3+Sr2+Rb+
Br-Se2-Ga3+Ca2+K+
Cl-S2-Al3+Mg2+Na+
F-O2-N3-Be2+Li+
H-
6
5
4
3
2
1
VIIAVIAVAIVAIIIAIIAIAPeriod
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What are the names of the following ionic compounds?
– BaO
– Cr2(SO4)3
BaO is barium oxide.Cr2(SO4)3 is chromium(III) sulfate or chromic sulfate.
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What are the chemical formulas for the following ionic compounds?
– potassium carbonate
– manganese(II) sulfate
The ions K+ and CO32- form K2CO3
The ions Mn2+ and SO42- form MnSO4
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What are the names of the following compounds?
– OF2
– S4N4
– BCl3
OF2 is oxygen difluoride
S4N4 is tetrasulfur tetranitride
BCl3 is boron trichloride
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What are the formulas for the following binary molecular compounds?
– carbon disulfide
– nitrogen tribromide
– dinitrogen tetrafluoride
The formula for carbon disulfide is CS2.
The formula for dinitrogen tetrafluoride is N2F4.
The formula for nitrogen tribromide is NBr3.
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A compound whose common name is green vitriol has the chemical formula FeSO4·7H2O. What is the chemical name of this compound?
FeSO4·7H2O is iron(II) sulfate heptahydrate.
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Calcium chloride hexahydrate is used to melt snow on roads. What is the chemical formula of the compound?
The chemical formula for calcium chloride hexahydrate is CaCl2·6H2O.
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Balance the following equations:
NH3 + O2 NO + H2O
C2H5OH + O2 CO2 + H2O
4NH3 + 5O2 4NO + 6H2O
C2H5OH + 3O2 2CO2 + 3H2O
Chapter 3
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Calculate the formula weight of the following compounds from their formulas. Report your answers to three significant figures.
– calcium hydroxide, Ca(OH)2
– methylamine, CH3NH2
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3 significant figures74.1 amu
3 significant figures31.1 amu
Total 74.095
2 O 2(16.00) = 32.00 amu
Ca(OH)2
1 Ca 1(40.08) = 40.08 amu
2 H 2(1.008) = 2.016 amu
CH3NH2
1 C 1(12.01) = 12.01 amu
5 H 5(1.008) = 5.040 amu1 N 1(14.01) = 14.01 amu
Total 31.060
Calculate the formula weight of the following compounds from their formulas. calcium hydroxide, Ca(OH)2
methylamine, CH3NH2
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A sample of nitric acid, HNO3, contains 0.253 mol HNO3. How many grams is this?
First, find the molar mass of HNO3:
1 H 1(1.008) = 1.0081 N 1(14.01) = 14.013 O 3(16.00) = 48.00
63.018 (2 decimal places)63.02 g/mol
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mole1
g63.02xmole0.253
figures)tsignifican(3
g 15.9
Next, using the molar mass, find the mass of 0.253 mole:
= 15.94406 g
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The average daily requirement of the essential amino acid leucine, C6H14O2N, is 2.2 g for an adult. What is the average daily requirement of leucine in moles?
First, find the molar mass of leucine:
6 C 6(12.01) = 72.062 O 2(16.00) = 32.001 N 1(14.01) = 14.0114 H 14(1.008) = 14.112
132.1822 decimal places
132.18 g/mol
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g132.18
mole1xg2.2
mol10x1.6643 2
figures)tsignifican(2
mol0.017ormol10x1.7 2
Next, find the number of moles in 2.2 g:
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mol1
atoms10x6.02x
g51.996
mol1xg10x1.0
236
First, find the molar mass of Cr:1 Cr 1(51.996) = 51.996 g/mol
Now, convert 1.0 x 10-6 grams to moles:
=1.157781368 x 1016 atoms
1.2 x 1016 atoms(2 significant figures)
The daily requirement of chromium in the human diet is 1.0 × 10-6 g. How many atoms of chromium does this represent?
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Lead(II) chromate, PbCrO4, is used as a paint pigment (chrome yellow). What is the percentage composition of lead(II) chromate?
First, find the molar mass of PbCrO4:
1 Pb 1(207.2) = 207.21 Cr 1(51.996) = 51.9964 O 4(16.00) = 64.00
323.196 (1 decimal place)323.2 g/mol
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64.11%100%xg323.20
g207.2:Pb
16.09%100%xg323.20
g51.996:Cr
19.80%100%xg323.20
g64.00:O
Now, convert each to percent composition:
Check:64.11 + 16.09 + 19.80 = 100.00 %
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Benzene has the empirical formula CH. Its molecular weight is 78.1 amu. What is its molecular formula?
613.02
78.1
amu3.02
amu 1.008) 12.01weightformulaEmpirical
1
(
Molecular formulaC6H6
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Hexamethylene is one of the materials used to produce a type of nylon. It is composed of 62.1% C, 13.8% H, and 24.1% N. Its molecular weight is 116 amu. What is its molecular formula?
Nmol1.720Ng14.01
Nmol1X Ng24.1
Hmol13.69Hg1.008
Hmol1X Hg13.8
Cmol5.171Cg12.01
Cmol1X Cg62.1
11.720
1.720
81.720
13.69
31.720
5.171
Empirical formulaC3H8N
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The empirical formula is C3H8N.
Molecular formula = (Empirical formula)n
Find the empirical formula weight:
3(12.01) + 8(1.008) + 1(14.01) = 58.104 amu
Molecular formula: C6H16N2
258.10
116 n
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Propane, C3H8, is normally a gas, but it is sold as a fuel compressed as a liquid in steel cylinders. The gas burns according to the following equation:
C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g)
How many grams of CO2 are produced when 20.0 g of propane is burned?
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Molar massesC3H8: 3(12.01) + 8(1.008) = 44.094 gCO2: 1(12.01) + 2(16.00) = 44.01 g
59.9 g CO2
(3 significant figures)
2
2
83
2
83
8383 COmol1
COg44.01
HCmol1
COmol3
HCg44.094
HCmol1HCg20.0 XXX
2COg359.8856987
C3H8(g) + 5O2(g) 3CO2(g) + 4H2O(g)
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Urea, CH4N2O, is used as a nitrogen fertilizer. It is manufactured from ammonia and carbon dioxide at high pressure and high temperature:
2NH3 + CO2(g) CH4N2O + H2O
In a laboratory experiment, 10.0 g NH3 and 10.0 g CO2 were added to a reaction vessel. What is the maximum quantity (in grams) of urea that can be obtained? How many grams of the excess reactant are left at the end of the reactions?
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2NH3 + CO2(g) CH4N2O + H2O
Molar masses: NH3 1(14.01) + 3(1.008) = 17.02 g CO2 1(12.01) + 2(16.00) =
44.01 g CH4N2O 1(12.01) + 4(1.008) + 2(14.01) + 1(16.00) = 60.06 g
CO2 is the limiting reactant. 13.6 g CH4N2O will be produced.
ONCHg13.6
ONCHmol1
ONCHg60.06
COmol1
ONCHmol1
COg44.01
COmol1COg10.0
24
24
24
2
24
2
22
XXX
ONCHg17.6
ONCHmol1
ONCHg60.06
NHmol2
ONCHmol1
NHg17.02
NHmol1NHg10.0
24
24
24
3
24
3
33
XXX
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10.0 g at start-7.73 g reacted 2.27 g remains
2.3 g NH3 is left unreacted.(1 decimal place)
reactedNHg7.73 3
3
3
2
3
2
22 NHmol1
NHg17.02
COmol1
NHmol2
COg44.01
COmol1COg10.0 XXX
3NHg7.73460577
To find the excess NH3, we find how much NH3 reacted:
Now subtract the amount reacted from the starting amount:
2NH3 + CO2(g) CH4N2O + H2O
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2NH3 + CO2(g) CH4N2O + H2O
When 10.0 g NH3 and 10.0 g CO2 are added to a reaction vessel, the limiting reactant is CO2. The theoretical yield is 13.6 g of urea. When this reaction was carried out, 9.3 g of urea was obtained. What is the percent yield?
Theoretical yield = 13.6 gActual yield = 9.3 g
= 68% yield(2 significant figures)
100%x g 13.6
g 9.3
Chapter 4
Chemical Reactions
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Determine whether each of the following reactions occurs. If it does, write the molecular, ionic, and net ionic equations.
KBr + MgSO4 NaOH + MgCl2 K3PO4 + CaCl2
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Classify the following as strong or weak acids or bases:
a. KOH
b. H2S
c. CH3NH2
d. HClO4
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Write the molecular, ionic, and net ionic equations for the neutralization of sulfurous acid, H2SO3, by potassium hydroxide, KOH.
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Write the molecular, ionic, and net ionic equations for the reaction of copper(II) carbonate with hydrochloric acid.
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Potassium permanganate, KMnO4, is a purple-colored compound; potassium manganate, K2MnO4, is a green-colored compound. Obtain the oxidation numbers of the manganese in these compounds.
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What is the oxidation number of Cr in dichromate, Cr2O7
2-?
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Balance the following oxidation-reduction reaction:
FeI3(aq) + Mg(s) Fe(s) + MgI2(aq)
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You place a 1.52 g of potassium dichromate, K2Cr2O7, into a 50.0 mL volumetric flask. You then add water to bring the solution up to the mark on the neck of the flask. What is the molarity of K2Cr2O7 in the solution?
Molar mass of K2Cr2O7 is 294 g.
L 10 x 50.0
g 294
mol 1 g 1.52
3- 0.103 M
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A solution of sodium chloride used for intravenous transfusion (physiological saline solution) has a concentration of 0.154 M NaCl. How many moles of NaCl are contained in 500. mL of physiological saline? How many grams of NaCl are in the 500. mL of solution?
NaClmol0.0770
L0.5000.154
Vmol
M
M
NaClg4.50
mol1
g58.4mol0.0770
g58.4NaClmassMolar
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A saturated stock solution of NaCl is 6.00 M. How much of this stock solution is needed to prepare 1.00 L of physiological saline solution (0.154 M)?
i
ffi
ffii
M
VMV
VMVM
mL25.7orL0.0257
6.00
L))(1.00(0.154
i
i
V
M
MV
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A soluble silver compound was analyzed for the percentage of silver by adding sodium chloride solution to precipitate the silver ion as silver chloride. If 1.583 g of silver compound gave 1.788 g of silver chloride, what is the mass percent of silver in the compound?
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Agmol1
Agg107.9 x
AgClmol1
Agmol1 x
AgClg143.32
AgClmol1 x AgClg1.788
= 1.346 g Ag in the compound
100% Xcompoundsilverg1.583
Agg1.346
= 85.03% Ag
Molar mass of silver chloride (AgCl) = 143.32 g
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Zinc sulfide reacts with hydrochloric acid to produce hydrogen sulfide gas:
ZnS(s) + 2HCl(aq) ZnCl2(aq) + H2S(g)
How many milliliters of 0.0512 M HCl are required to react with 0.392 g ZnS?
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Molar mass of ZnS = 97.47 g
= 0.157 L = 157 mL HCl solution
HClmol0.0512
solutionL1 x
ZnSmol1
HClmol2 x
ZnSg97.47
ZnSmol1 x ZnSg0.392
ZnS(s) + 2HCl(aq) ZnCl2(aq) + H2S(g)
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A dilute solution of hydrogen peroxide is sold in drugstores as a mild antiseptic. A typical solution was analyzed for the percentage of hydrogen peroxide by titrating it with potassium permanganate:
5H2O2(aq) + 2KMnO4(aq) + 6H+(aq) 8H2O(l) + 5O2(g) + 2K+(aq) + 2Mn2+(aq)
What is the mass percent of H2O2 in a solution if 57.5 g of solution required 38.9 mL of 0.534 M KMnO4 for its titration?
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22
22
4
2243
OHmol1
OHg34.01 x
KMnOmol2
OHmol5 x
L1
KMnOmol0.534 x L10x38.9
Molar mass of H2O2 = 34.01 g
= 1.77 g H2O2
100% Xsolutiong57.5
OHg1.77 22
= 3.07% H2O2
5H2O2(aq) + 2KMnO4(aq) + 6H+(aq) 8H2O(l) + 5O2(g) + 2K+(aq) + 2Mn2+(aq)
Chapter 5
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mmHg)(359
mmHg)mL)(751(38.7f V
= 81.0 mL(3 significant figures)
f
iif P
VPV
A volume of oxygen gas occupies 38.7 mL at 751 mmHg and 21°C. What is the volume if the pressure changes to 359 mmHg while the temperature remains constant?
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You prepared carbon dioxide by adding HCl(aq) to marble chips, CaCO3. According to your calculations, you should obtain 79.4 mL of CO2 at 0°C and 760 mmHg. How many milliliters of gas would you obtain at 27°C?
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Vi = 79.4 mLPi = 760 mmHgTi = 0°C = 273 K
Vf = ?Pf = 760 mmHgTf = 27°C = 300. K
K)(273
mL)K)(79.4(300.f V
= 87.3 mL(3 significant figures)
i
iff T
VTV
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Divers working from a North Sea drilling platform experience pressure of 5.0 × 101 atm at a depth of 5.0 × 102 m. If a balloon is inflated to a volume of 5.0 L (the volume of the lung) at that depth at a water temperature of 4°C, what would the volume of the balloon be on the surface (1.0 atm pressure) at a temperature of 11°C?
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Vi = 5.0 LPi = 5.0 × 101 atmTi = 4°C = 277 K
Vf = ?Pf = 1.0 atmTf = 11°C = 284. K
fi
iiff PT
VPTV
atm)K)(1.0(277
L)atm)(5.010xK)(5.0(284 1
f V
= 2.6 x 102 L(2 significant figures)
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Ideal Gas Law
The ideal gas law is given by the equation
PV=nRT
The molar gas constant, R, is the constant of proportionality that relates the molar volume of a gas to T/P.
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A 50.0 L cylinder of nitrogen, N2, has a pressure of 17.1 atm at 23°C. What is the mass of nitrogen in the cylinder?
V = 50.0 LP = 17.1 atmT = 23°C = 296 K
RT
PVn
mol20.35
K)(296
Kmol
atmL0.08206
L)atm)(50.0(17.1n
mass = 986 g(3 significant figures)mol
g28.01X mol35.20mass
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What is the density of methane gas (natural gas), CH4, at 125°C and 3.50 atm?
Mm = 16.04 g/molP = 3.50 atmT = 125°C = 398 K
RT
PMd m
K)(398Kmol
atmL0.08206
atm))(3.50mol
g(16.04
dfigures)tsignifican(3L
g1.72d
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A 500.0-mL flask containing a sample of octane (a component of gasoline) is placed in a boiling water bath in Denver, where the atmospheric pressure is 634 mmHg and water boils at 95.0°C. The mass of the vapor required to fill the flask is 1.57 g. What is the molar mass of octane? (Note: The empirical formula of octane is C4H9.) What is the molecular formula of octane?
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P = 634 mmHg = 0.8342 atm
P
dRTM m
atm)(0.8342
K368.2Kmol
atmL0.08206
L
g3.140
m
M
figures)tsignifican(3mol
g114mM
d = 1.57 g/0.5000 L = 3.140 g/L
T = 95.0°C = 368.2 K
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2
mol
g57
mol
g114
n
Molecular formula: C8H18
Molar mass = 114 g/molEmpirical formula: C4H9
Empirical formula molar mass = 57 g/mol
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When a 2.0-L bottle of concentrated HCl was spilled, 1.2 kg of CaCO3 was required to neutralize the spill. What volume of CO2 was released by the neutralization at 735 mmHg and 20.°C?
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First, write the balanced chemical equation:
CaCO3(s) + 2HCl(aq) CaCl2(aq) + H2O(l) + CO2(g)
3
2
3
33
3
CaCOmol1
COmol1
CaCOg100.09
CaCOmol1CaCOg10x1.2 XX
Moles of CO2 produced = 12 mol
Second, calculate the moles of CO2 produced:
Molar mass of CaCO3 = 100.09 g/mol
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n = 12 molP = 735 mmHg = 0.967 atmT = 20°C = 293 K
P
nRTV
atm)(0.967
K)(293Kmol
atmL0.08206mol12
V
= 3.0 × 102 L(2 significant figures)
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A 100.0-mL sample of air exhaled from the lungs is analyzed and found to contain 0.0830 g N2, 0.0194 g O2, 0.00640 g CO2, and 0.00441 g water vapor at 35°C. What is the partial pressure of each component and the total pressure of the sample?
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mL10
L1mL100.0
K308Kmol
atmL0.08206
Ng28.01
Nmol1Ng0.0830
2
3
2
22
NP
mL10
L1mL100.0
K308Kmol
atmL0.08206
Og32.00
Omol1Og0.0194
2
3
2
22
OP
mL10
L1mL100.0
K308Kmol
atmL0.08206
COg44.01
COmol1COg0.00640
2
3
2
22
COP
mL10
L1mL100.0
K308Kmol
atmL0.08206
OHg18.01
OHmol1OHg0.00441
2
3
2
22
OHP
atm0.749
atm0.153
atm0.0368
atm0.0619
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atm0.7492N P
atm0.1532O P
atm0.03682CO P
atm0.0619OH2P
OHCOON 2222PPPPP
P = 1.00 atm
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The partial pressure of air in the alveoli (the air sacs in the lungs) is as follows: nitrogen, 570.0 mmHg; oxygen, 103.0 mmHg; carbon dioxide, 40.0 mmHg; and water vapor, 47.0 mmHg. What is the mole fraction of each component of the alveolar air?
OHCOON 2222PPPPP
570.0 mmHg103.0 mmHg
40.0 mmHg47.0 mmHg
P = 760.0 mmHg
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Mole fraction of N2
Mole fraction of H2OMole fraction of CO2
Mole fraction of O2
mmHg760.0
mmHg47.0
mmHg760.0
mmHg40.0
mmHg760.0
mmHg103.0
mmHg760.0
mmHg570.0
Mole fraction N2 = 0.7500
Mole fraction O2 = 0.1355
Mole fraction CO2 = 0.0526
Mole fraction H2O= 0.0618
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You prepare nitrogen gas by heating ammonium nitrite:
NH4NO2(s) N2(g) + 2H2O(l)
If you collected the nitrogen over water at 23°C and 727 mmHg, how many liters of gas would you obtain from 5.68 g NH4NO2?
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P = 727 mmHgPvapor = 21.1 mmHgPgas = 706 mmHgT = 23°C = 296 K P
nRTV
Molar mass NH4NO2
= 64.04 g/mol
24
2
24
24 24
NONHmol1
Nmol1
NONHg64.04
NONHmol1NONHg5.68 XX
= 0.08869 mol N2 gas
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P = 727 mmHgPvapor = 21.1 mmHgPgas = 706 mmHgT = 23°C = 296 Kn = 0.08869 mol
P
nRTV
mmHg760
atm1 xmmHg706
K)(296Kmol
atmL0.08206mol0.0887
V
= 2.32 L of N2
(3 significant figures)
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mol
kg0.04401
K296Kmol
s
mkg
8.314532
2
rmsu
2
25
rmss
m1.68x10u
s
mx104.10 2
rms u
2
2
s
mkgJ
Recall
mM
RTu
3rms
What is the rms speed of carbon dioxide molecules in a container at 23°C?
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Both hydrogen and helium have been used as the buoyant gas in blimps. If a small leak were to occur, which gas would effuse more rapidly and by what factor?
Hydrogen will diffuse more quickly by a factor of 1.4.
2.016
4.002
4.002
12.016
1
HeRate
HRate 2
Chapter 6
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A person weighing 75.0 kg (165 lbs) runs a course at 1.78 m/s (4.00 mph). What is the person’s kinetic energy?
2
K s
m1.78kg)(75.0
2
1
E
m = 75.0 kgV = 1.78 m/s
EK = ½ mv2
figures)tsignifican(3
J119s
mkg119
2
2
K
E
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In an endothermic reaction:
The reaction vessel cools.
Heat is absorbed.
Energy is added to the system.
q is positive.
In an exothermic reaction:
The reaction vessel warms.
Heat is evolved.
Energy is subtracted from the system.
q is negative.
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S8(s) + 8O2(g) 8SO2(g)
S8(s) + 8O2(g) 8SO2(g); H = –2.39 × 103 kJ
kJ10 2.39Δ
Smol1
Sg256.52
Sg1
kJ9.31Δ
3
8
8
8
H
H
Sulfur, S8, burns in air to produce sulfur dioxide. The reaction evolves 9.31 kJ of heat per gram of sulfur at constant pressure. Write the thermochemical equation for this reaction.
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8
3
8
88 Smol1
kJ10x2.39
Sg256.5
Smol1Sg15.0
q
q = –1.40 × 102 kJ
Molar mass of S8 = 256.52 g
You burn 15.0 g sulfur in air. How much heat evolves from this amount of sulfur? The thermochemical equation is
S8(s) + 8O2(g) 8SO2(g); H = -2.39 x 103 kJ
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The daily energy requirement for a 20-year-old man weighing 67 kg is 1.3 x 104 kJ. For a 20-year-old woman weighing 58 kg, the daily requirement is
8.8 x 103 kJ. If all this energy were to be provided by the combustion of glucose, C6H12O6, how many grams of glucose would have to be consumed by the man and the woman per day?
C6H12O6(s) + 6O2(g) 6CO2(g) + 6H2O(l);Ho = -2.82 x 103 kJ
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C6H12O6(s) + 6O2(g) 6CO2(g) + 6H2O(l);
H = -2.82 x 103 kJ
glucosemol1
glucoseg180.2
kJ2.82x10
glucosemol1kJ1.3x10
34
glucose m
For a 20-year-old man weighing 67 kg:
= 830 g glucose required(2 significant figures)
glucosemol1
glucoseg180.2
kJ2.82x10
glucosemol1kJ8.8x10
33
glucose m
For a 20-year-old woman weighing 58 kg:
= 560 g glucose required(2 significant figures)
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A piece of zinc weighing 35.8 g was heated from 20.00°C to 28.00°C. How much heat was required? The specific heat of zinc is 0.388 J/(g°C).
m = 35.8 gs = 0.388 J/(g°C)t = 28.00°C – 20.00°C = 8.00°C
q = m · s · t
C8.00Cg
J0.388g35.8
q
q = 111 J(3 significant figures)
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Nitromethane, CH3NO2, an organic solvent burns in oxygen according to the following reaction:
CH3NO2(g) + 3/4O2(g) CO2(g) + 3/2H2O(l) + 1/2N2(g)
You place 1.724 g of nitromethane in a calorimeter with oxygen and ignite it. The temperature of the calorimeter increases from 22.23°C to 28.81°C. The heat capacity of the calorimeter was determined to be 3.044 kJ/°C. Write the thermochemical equation for the reaction.
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We first find the heat evolved for the 1.724 g of nitromethane, CH3NO2.
Now, covert that to the heat evolved per mole by using the molar mass of nitromethane, 61.04 g.
23
23
23rxn NOCHmol1
NOCHg61.04
NOCHg1.724
kJ 20.03- q
H = –709 kJ
kJ 20.03 C22.23C28.81C
kJ3.044
Δ
rxn
calrxn
q
tCq
CH3NO2(l) + ¾O2(g) CO2(g) + 3/2H2O(l) + ½N2(g); H = –709 kJ
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What is the enthalpy of reaction, H, for the reaction of calcium metal with water?
Ca(s) + 2H2O(l) Ca2+(aq) + 2OH-(aq) + H2(g)
This reaction occurs very slowly, so it is impractical to measure H directly. However, the following facts are known:
H+(aq) + OH-(aq) H2O(l); H = –55.9 kJCa(s) + 2H+(aq)
Ca2+(aq) + H2(g); H = –543.0 kJ
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Ca(s) + 2H2O(l) Ca2+(aq) + 2OH-(aq) + H2(g)
2H2O(l) 2H+(aq) + 2OH-(aq); H = +111.8 kJ
Ca(s) + 2H+(aq) Ca2+(aq) + H2(g); H = –543.0 kJ
Ca(s) + 2H2O(l) Ca2+(aq) + 2OH-(aq) + H2(g); H = –431.2 kJ
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We want H° for the reaction:CH3OH(l) CH3OH(g)
mol
kJ200.7Δ:methanolgaseousFor
mol
kJ238.7Δ:methanolliquidFor
f
f
H
H
reactants
fproducts
freaction ΔΔΔ HnHnH
mol
kJ238.7 mol 1
mol
kJ200.7 mol 1Δ vapH = +38.0 kJ
What is the heat of vaporization of methanol, CH3OH, at 25°C and 1 atm?
Use standard enthalpies of formation (Appendix C).
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Methyl alcohol, CH3OH, is toxic because liver enzymes oxidize it to formaldehyde, HCHO, which can coagulate protein. Calculate Ho for the following reaction:
2CH3OH(aq) + O2(g) 2HCHO(aq) + 2H2O(l)
Standard enthalpies of formation, :ofΔH
CH3OH(aq): -245.9 kJ/molHCHO(aq): -150.2 kJ/molH2O(l): -285.8 kJ/mol
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We want H° for the reaction:2CH3OH(aq) + O2(aq) 2HCHO(aq) + 2H2O(l)
reactants
fproducts
freaction ΔΔΔ HnHnH
mol
kJ0mol 1
mol
kJ245.9 mol 2
mol
kJ285.8-mol 2
mol
kJ150.2 mol 2Δ o
reactonH
kJ 491.8kJ 571.6kJ 300.4 Δ oreaction H
kJ 491.8kJ 872.0Δ oreaction H
kJ 380.2Δ oreaction H
Chapter 7
Quantum Theory of An Atome
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What is the wavelength of blue light with a frequency of 6.4 × 1014/s?
= 6.4 × 1014/sc = 3.00 × 108 m/s
c = so = c/
= 4.7 × 10-7 m
s
110x6.4
s
m10x3.00
λ14
8
c
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What is the frequency of light having a wavelength of 681 nm?
= 681 nm = 6.81 × 10-7 mc = 3.00 × 108 m/s
c = so = c/
v = 4.41 × 1014 /s
m10x6.81s
m10x3.00
7
8
c
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The range of frequencies and wavelengths of electromagnetic radiation is called the electromagnetic spectrum.
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The blue–green line of the hydrogen atom spectrum has a wavelength of 486 nm. What is the energy of a photon of this light?
= 486 nm = 4.86 × 10-7 mc = 3.00 × 108 m/sh = 6.63 × 10-34 J · s
E = h andc = so E = hc/
E = 4.09 × 10-19 J
m10x4.86
s
m10x3.00Js6.63x10
λ 7
834
hc
E
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What is the wavelength of the light emitted when the electron in a hydrogen atom undergoes a transition from n = 6 to n = 3?
ni = 6nf = 3RH = 2.179 × 10-18 J
J10x1.816-
s
m10x2.998sJ10x6.626
λ19
834
= -1.816 x 10-19 J
1.094 × 10-6 m
soλ
Δhc
E E
hc
Δλ
22E
6
1
3
1J10x2.179Δ 18
2i
2f
H
11Δ
nnRE
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Compare the wavelengths of (a) an electron traveling at a speed that is one-hundredth the speed of light and (b) a baseball of mass 0.145 kg having a speed of 26.8 m/s (60 mph).
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Electronme = 9.11 × 10-31 kg; v = 3.00 × 106 m/s
Baseballm = 0.145 kg; v = 26.8 m/s
s
m10x3.00kg10x9.11
sJ10x6.63λ
631
34
2.43 × 10-10 m
s
m26.8kg0.145
sJ10x6.63λ
34
1.71 × 10-34 m
Comment: This is such an exceedingly small wavelength that the wave properties of a baseball cannot be detected by any existing measuring device.
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Which of the following are permissible sets of quantum numbers?
n = 4, l = 4, ml = 0, ms = ½
n = 3, l = 2, ml = 1, ms = -½
n = 2, l = 0, ml = 0, ms = ³/²
n = 5, l = 3, ml = -3, ms = ½(a) Not permitted. When n = 4, the maximum
value of l is 3.(b) Permitted.(c) Not permitted; ms can only be +½ or –½. (b) Permitted.
Chapter 8
Electron Configuration and Periodicity
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The building-up principle (or aufbau principle) is a scheme used to reproduce the ground-state electron configurations by successively filling subshells with electrons in a specific order (the building-up order).
This order generally corresponds to filling the orbitals from lowest to highest energy. Note that these energies are the total energy of the atom rather than the energy of the subshells alone.
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1s
2s 2p
3s 3p 3d
4s 4p 4d4f
5s 5p 5d5f
6s 6p 6d
7s 7pThis results in the following order:
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p
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Another way to learn the building-up order is to correlate each subshell with a position on the periodic table.
The principal quantum number, n, correlates with the period number.
Groups IA and IIA correspond to the s subshell; Groups IIIA through VIIIA correspond to the p subshell; the “B” groups correspond to the d subshell; and the bottom two rows correspond to the f subshell. This is shown on the next slide.
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Write the complete electron configuration of the arsenic atom, As, using the building-up principle.
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p3
For arsenic, As, Z = 33.
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What are the electron configurations for the valence electrons of arsenic and zinc?
Arsenic is in period 4, Group VA.Its valence configuration is 4s24p3.
Zinc, Z = 30, is a transition metal in the first transition series. Its noble-gas core is Ar, Z = 18.Its valence configuration is
4s23d10.
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Write an orbital diagram for the ground state of the nickel atom.
3s 3p
1s 2s 2p
4s 3d
For nickel, Z = 28.
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Which of the following electron configurations or orbital diagrams are allowed and which are not allowed by the Pauli exclusion principle? If they are not allowed, explain why?
a. 1s22s12p3
b. 1s22s12p8
c. 1s22s22p63s23p63d8 d. 1s22s22p63s23p63d11
e.
1s 2s
a. Allowed; excited.b. p8 is not allowed.c. Allowed.d. d11 is not allowed.e. Not allowed; electrons in
one orbital must have opposite spins.
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A representation of atomic radii is shown below.
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Refer to a periodic table and arrange the following elements in order of increasing atomic radius: Br, Se, Te.
Te is larger than Se.Se is larger than Br.
Br < Se < Te
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The size of each sphere indicates the size of the ionization energy in the figure below.
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Refer to a periodic table and arrange the following elements in order of increasing ionization energy: As, Br, Sb.
Sb is larger than As.As is larger than Br.
Ionization energies: Sb < As < Br
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The element is in Group IIA.
The electron affinity is > 0, so the element must be in Group IIA or VIIIA.
The dramatic difference in ionization energies is at the third ionization.
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R is arsenic, As.
For R2O5 oxides, R must be in Group VA.R is a metalloid, so R could be As or Sb.The oxide is acidic, so
Chapter 9
Ionic and Covalent Bonding
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Table 9.1 illustrates the Lewis electron-dot symbols for second- and third-period atoms.
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Give the electron configuration and the Lewis symbol for the chloride ion, Cl-.
Cl -][
For chlorine, Cl, Z = 17, so the Cl- ion has 18 electrons. The electron configuration for Cl- is
1s2 2s2 2p6 3s2 3p6
The Lewis symbol for Cl- is
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Give the electron configurations of Mn and Mn2+.
Manganese, Z = 25, has 25 electrons;. Its electron configuration is
1s2 2s2 2p6 3s2 3p6 4s23d5
Mn2+ has 23 electrons. When ionized, Mn loses the 4s electrons first; the electron configuration for Mn2+ is
1s2 2s2 2p6 3s23p6 3d5
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Using the periodic table only, arrange the following ions in order of increasing ionic radius: Br-, Se2-, Sr2+. These ions are isoelectronic,
so their size decreases with increasing atomic number:
Sr2+ < Br- < Se2-
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Using electronegativities, arrange the following bonds in order by increasing polarity:
C—N
Na—F
O—H
For Na—F, the difference is 4.0 (F) – 0.9 (Na) = 3.1.
For C—N, the difference is 3.0 (N) – 2.5 (C) = 0.5.
For O—H, the difference is 3.5 (O) – 2.1 (H) = 1.4.
C—N <Bond polarities: O—H < Na—F
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Writing Lewis Electron-Dot Formulas
Calculate the number of valence electrons.
Write the skeleton structure of the molecule or ion. The central atom is the one with less electronegativity.
Distribute electrons to the atoms surrounding the central atom or atoms to satisfy the octet rule.
Distribute the remaining electrons as pairs to the central atom or atoms.
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Write the electron dot formulas for the following:
a. OF2
b. NF3
c. NH2OH, hydroxylamine
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a. Count the valence electrons in OF2:
O 1(6)
F 2(7)
20 valence electrons
O is the central atom (it is less electronegative). Now, we distribute the remaining 16 electrons, beginning with the outer atoms. The last four electrons go on O.
OF F
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b. Count the valence electrons in NF3:
N 1(5)
F 3(7)
26 valence electrons
N is the central atom (it is less electronegative). Now, we distribute the remaining 20 electrons, beginning with the outer atoms. The last two electrons go on N.
F FN
F
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c. Count the electrons in NH2OH:
N 1(5)
H 3(1)
O 1(6)
14 valence electrons
N is the central atom (it is less electronegative than O). Now, we distribute the remaining six electrons, beginning with the outer atoms. The last two electrons go on N.
H
NH HO
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Write electron-dot formulas for the following:
a. CO2
b. HCN
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a. Count the electrons in CO2:
C 1(4)
O 2(6)
16 valence electrons
C is the central atom. Now, we distribute the remaining 12 electrons, beginning with the outer atoms.
Carbon does not have an octet, so two of the lone pairs shift to become a bonding pair, forming double bonds.
OO CO O
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b. Count the electrons in HCN:H 1(1)C 1(4)N 1(5)
10 valence electrons.
C is the central atom. The remaining electrons go on N.
Carbon does not have an octet, so two of the lone pairs shift to become a bonding pair, forming a triple bond.
CH NN
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Phosphorus pentachloride exists in solid state as the ionic compound [PCl4]+[PCl6]-; it exists in the gas phase as the PCl5 molecule. Write the Lewis formula of the PCl4+ ion.
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Count the valence electrons in PCl4+:
P 1(5)
Cl 4(7)
-1
32
P is the central atom. The remaining 24 nonbonding electrons are placed on Cl atoms. Add square brackets with the charge around the ion.
Cl
Cl
ClCl P
+
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Count the valence electrons in IF5:
I 1(7)
F 5(7)
42 valence electrons
I is the central atom. Thirty-two electrons remain; they first complete F octets. The remaining electrons go on I.
F
F
F
I
F
F
Give the Lewis formula of the IF5 molecule.
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Compare the formal charges for the following electron-dot formulas of CO2.
CO O
For the left structure: For the right structure:
O: 6 – 2 – 4 = 0C: 4 – 4 – 0 = 0
The left structure is better.
CO O
Formal charge = group number – (number of bond pairs) – (number of nonbonding electrons)
C: 4 – 4 – 0 = 0O: 6 – 1 – 6 = –1O: 6 – 3 – 2 = +1
Chapter 10
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The diagrams below illustrate molecular geometry and the impact of lone pairs on it for linear and trigonal planar electron-pair arrangements.
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Molecular geometries with a tetrahedral electron-pair arrangement are illustrated below.
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Molecular geometries for the trigonal bipyramidal electron-pair arrangement are shown on the next slide.
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Molecular geometries for the octahedral electron-pair arrangement are shown below.
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Use the VSEPR model to predict the geometries of the following molecules:
a. AsF3
b. PH4+
c. BCl3
a. Trigonal pyramidal.b. Tetrahedral.c. Trigonal planar.
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Using the VSEPR model, predict the geometry of the following species:
a. ICl3b. ICl4-
a. T-shaped.b. Square planar.
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Which of the following molecules would be expected to have a zero dipole moment?
a. GeF4
b. SF2
c. XeF2
d. AsF3
a. GeF4 tetrahedral molecular geometryzero dipole moment
b. SF2 bent molecular geometrynonzero dipole moment
c. XeF2 linear molecular geometryzero dipole moment
d. AsF3 trigonal pyramidal molecular geometrynonzero dipole moment
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Hybrid orbitals have definite directional characteristics, as described in Table 10.2.
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Use valence bond theory to describe the bonding about an N atom in N2H4.
N N
F
F
F
F
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The sp3 hybridized N atom is
1s sp3
Consider one N in N2F4: the two N—F bonds are formed by the overlap of a half-filled sp3 orbital with a half-filled 2p orbital on F. The N—N bond forms from the overlap of a half-filled sp3 orbital on each. The lone pair occupies one sp3 orbital.
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Use valence bond theory to describe the bonding in the ClF2
- ion.
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3dsp3d
The sp3d hybridized orbital diagram for the Cl- ion is
Two Cl—F bonds are formed from the overlap of two half-filled sp3d orbitals with half-filled 2p orbitals on the F atom. These use the axial positions of the trigonal bipyramid.
Three lone pairs occupy three sp3d orbitals. These are in the equatorial position of the trigonal bipyramid.
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Describe the bonding about the C atom in formaldehyde, CH2O, using valence bond theory.
C
H
O
H
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1s sp2 2p
After hybridization, the orbital diagram for C is
The C—H bonds are formed from the overlap of two C sp2 hybrid orbitals with the 1s orbital on the H atoms.
The C—O bond is formed from the overlap of one sp2 hybrid orbital and one O half-filled p orbital.
The C—O bond is formed from the sideways overlap of the C 2p orbital and an O 2p orbital.
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Give the orbital diagram and electron configuration of the F2 molecule.
Is the molecular substance diamagnetic or paramagnetic?
What is the order of the bond in F2?
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F2 has 18 electrons. The KK shell holds 4 electrons so 14 remain.
The molecular electron configuration isKK(2s)2(2s)2(2p)4(2p)2 (*2p)4
The bond order is ½(8 - 6) = 1.The molecule is diamagnetic.
For F2 and O2, 2p is lower in energy than 2p. This order would not affect the determination of bond order and magnetic properties for these molecules.
s2 s2*
p2 p2 p2 p2
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A number of compounds of the nitrosonium ion, NO+, are known, including nitrosonium hydrogen sulfate, (NO+)(HSO4
-). Use the molecular orbitals similar to those of homonuclear diatomic molecules and obtain the orbital diagram, electron configuration, bond order, and magnetic characteristics of the NO+ ion.
Note: The stability of the ion results from the loss of an antibonding electron from NO.
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NO+ has 14 electrons. The KK shell holds 4 electrons, leaving 10 electrons for bonding.
The molecular electron configuration isKK(2s)2(2s)2(2p)4(2p)2
The bond order is ½(8 - 2) = 3.
The ion has a diamagnetic molecular orbital electron configuration.
s2 s2*
p2 p2 p2 p2
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The valence-shell electron-pair repulsion (VSEPR) model predicts the shapes of molecules and ions by assuming that the valence-shell electron pairs are arranged about each atom so that electron pairs are kept as far away from one another as possible, thereby minimizing electron pair repulsions.
The diagram on the next slide illustrates this.
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Two electron pairs are 180° apart ( a linear arrangement).
Three electron pairs are 120° apart in one plane (a trigonal planar arrangement).
Four electron pairs are 109.5° apart in three dimensions (a tetrahedral arrangement).
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Five electron pairs are arranged with three pairs in a plane 120° apart and two pairs at 90°to the plane and 180° to each other (a trigonal bipyramidal arrangement).
Six electron pairs are 90° apart (an octahedral arrangement).
This is illustrated on the next slide.
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These arrangements are illustrated below with balloons and models of molecules for each.