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Chapter 7 Answers and Solutions
7
Answers and Solutions to Text Problems
7.1
A mole is the amount of a substance that contains 6.02 x 1023 items. For example, one mole of
water contains 6.02 ✕1023 molecules of water.
7.2
Avogadro’s number is 6.02 ✕1023, which equals the number of items in one mole.
7.3
a. One mole of carbon contains 6.02 ✕ 1023 atoms of carbon.
b. One mole of iron contains 6.02 ✕ 1023 atoms of iron.
✕ 6.02 ✕1023 atoms Fe
= 1.2 ✕ 1024 atoms Fe
2.0 moles Fe
1 mole Fe
c. 0.50 moles CO2
✕ 6.02 ✕ 1023 molecules CO2 = 3.0 ✕ 1023 molecules CO2
1 mole CO 2
7.4
a. 2.5 moles S
b. 0.020 mole Ag
c. 8.0 moles H2O
7.5
✕
6.02 x 1023 atoms S
= 1.5 ✕ 1024 atoms S
1 mole S
✕ 6.02 x 1023 atoms Ag
= 1.2 ✕ 1022 atoms Ag
1 mole Ag
✕ 6.02 x 1023 molecules H2O = 4.8 ✕ 1024 molecules H2O
1 mole H2O
The subscripts indicate the moles of each element in one mole of that compound.
a. 24 moles of H
b. 5.0 moles quinine
✕ 20 moles C atoms ✕ 6.02 x 1023 atoms C = 6.0 ✕ 1025 atoms C
1 mole quinine
1 mole C
c. 0.020 moles quinine ✕ 2 moles N atoms ✕ 6.02 ✕ 1023 atoms N = 2.4 ✕ 1022 atoms N
1 mole quinine
1 mole N atoms
7.6
The subscripts indicate the moles of each element in one mole of that compound.
= 9.0 moles S
a. 3.0 moles Al2(SO4)3 ✕ 3 moles S atoms
1 mole Al2(SO4)3
b. 0.40 moles Al2(SO4)3 ✕ 2 moles Al ions ✕ 6.02 ✕ 1023 Al ions = 4.8 ✕ 1023 Al ions
1 mole q Al2(SO4)3 1 mole Al ions
c. 1.5 moles Al2(SO4)3 ✕ 3 moles SO4 ions ✕ 6.02 ✕1023 SO4 ions = 2.7 ✕ 1024 SO42- ions
1 mole Al2(SO4)3
1 mole SO4 ions
7.7
a. 2.5 moles of C atoms ✕ 6.02 x 1023 atoms of C = 1.5 x 1024 atoms C
1 mole of C atoms
b. 2.0 moles PCl3 ✕ 3 moles Cl atoms ✕ 6.02 x 1023 atoms Cl = 3.6 x 1024 atoms Cl
1 mole PCl3
1 mole Cl atoms
c. 5.0 x 1024 atoms O ✕ 1 moles O atoms
✕ 1 mole SO3
= 2.8 moles SO3
6.02 x 1023 atoms O
3 mole O atoms
Chemical Quantities
7.8
a. 1.5 moles of Au atoms ✕ 6.02 ✕ 1023 atoms of Au
1 mole of Au atoms
= 9.0 ✕ 1023 atoms Au
b. 0.30 moles NBr3 ✕ 3 moles Br atoms ✕6.02 x 1023 atoms Br
1 mole NBr3
1 mole Br atoms
c. 5.0 ✕ 1024 H atoms ✕ 1 mole H atoms
✕ 1 mole C2H6O
6.02 x 1023 H atoms 6 moles H atoms
7.9
= 5.4 ✕ 1023 atoms Br
= 1.4 moles C2H6O
a. 1 mole of Na and 1 mole of Cl:
23.0 g + 35.5 g = 58.5 g/mole NaCl
b. 2 mole of Fe and 3 moles of O:
111.8 g + 48.0 g = 159.8 g/mole Fe2O3
c. 2 mole of Li and 1 mole of C and 3 moles of O:
13.8 g + 12.0 g + 48.0 g = 73.8 g/mole Li2CO3
d. 2 mole of Al and 3 moles of S and 12 moles of O:
54.0 g + 96.3 g + 192.0 g = 342.3 g/mole Al2(SO4)3
e. 1 mole of Mg and 2 moles of O and 2 moles of H:
24.3 g + 32.0 g + 2.0 g = 58.3 g/mole Mg(OH)2
f. 16 moles of C and 19 moles of H and 3 moles of N and 5 moles of O and 1 mole of S:
192.0 g + 19.0 g + 42.0 g + 80.0 g + 32.1 g = 365.1 g/mole C16H19N3O5S
7.10
a. 1 mole of Fe and 1 mole of S and 4 moles of O:
55.9 g + 32.1 g + 64.0 g = 152.0 g/mole FeSO4
b. 2 moles of Al and 3 moles of O:
54.0 g + 48.0 g = 102.0 g/mole Al2O3
c. 7 moles of C, 5 moles of H, 1 mole of N, 3 moles of O, and 1 mole S:
84.0 g + 5.0 g + 14.0 g + 48.0 g and 32.1 = 183.1 g/mole C7H5NO3S
d. 3 moles of C and 8 moles of H and 1 mole of O:
36.0 g + 8.0 g + 16.0 g = 60.0 g/mole C3H8O
e. 2 moles of N and 8 moles of H and 1 mole of C and 3 moles of O:
28.0 g + 8.0 g + 12.0 g + 48.0 g = 96.0 g/mole (NH4)2CO3
f. 1 mole of Zn and 4 moles of C and 6 moles of H and 4 moles of O:
65.4 g + 48.0 g + 6.0 g + 64.0 g = 183.4 g/mole Zn(C2H3O2)2
7.11
a. 2.00 mole Na
✕
23.0 g Na
1 mole Na
= 46.0 g Na
b. 2.80 mole Ca
✕
40.1 g Ca
1 mole Ca
= 112 g Ca
c. 0.125 mole Sn
✕
118.7 g Sn
1 mole Sn
= 14.8 g Sn
Chapter 7 Answers and Solutions
7.12
7.13
7.14
7.15
a. 1.50 mole K
✕
39.1 g K
1 mole K
= 58.7 g K
b. 2.5 mole C
✕
= 30. g C
c. 0.25 mole P
✕
12.0 g C
1 mole C
31.0 g P
1 mole P
a. 0.500 mole NaCl
✕
58.5 g NaCl
1 mole NaCl
= 29.3 g NaCl
b. 1.75 mole Na2O
✕
62.0 g Na2O
1 mole Na2O
= 109 g Na2O
c. 0.225 mole H2O
✕
18.0 g H2O
1 mole H2O
= 4.05 g H2O
a. 2.0 mole MgCl2
✕
95.3 g MgCl2
1 mole MgCl2
= 190 g MgCl2
b. 3.5 mole C3H8
✕
44.0 g C3H8
1 mole C3H8
= 150 g C3H8
c. 5.00 mole C2H6O
✕
46.0 g C2H6O = 230. g C2H6O (2.30 ✕ 102 g)
1 mole C2H6O
a. 0.500 mole K
✕
39.1 g K
1 mole K
= 19.6 g K
b. 0.500 mole Cl2
✕
71.0 g Cl2
1 mole Cl2
= 35.5 g Cl2
c. 0.500 mole Na2CO3 ✕
7.16
7.17
7.18
= 7.8 g P
106.0 g Na2CO3 = 53.0 g Na2CO3
1 mole Na2CO3
a. 2.25 mole N2
✕
28.0 g N2
1 mole N2
= 63.0 g N2
b. 2.25 mole NaBr
✕
102.9 g NaBr
1 mole NaBr
= 232 g NaBr
c. 2.25 mole C6H14
✕
86.0 g C6H14
1 mole C6H14
= 194 g C6H14
a. 5.00 mole MgSO4
✕
120.4 g MgSO4 = 602 g MgSO4
1 mole MgSO4
b. 0.25 mole CO2
✕
44.0 g CO2
1 mole CO2
= 11 g CO2
a. 0.25 mole C3H6
✕
42.0 g C3H6
1 mole C3H6
= 11 g C3H6
b. 0.025 mole C15H22ClNO2
✕
283.5 g C15H22ClNO2 = 7.1 g C15H22ClNO2
1 mole C15H22ClNO2
Chemical Quantities
7.19
7.20
7.21
✕
1 mole Ag
107.9 g Ag
= 0.463 mole Ag
b. 0.200 g C
✕
1 mole C
12.0 g C
= 0.0167 mole C
c. 15.0 g NH3
✕
1 mole NH3
17.0 g NH3
= 0.882 mole NH3
d. 75.0 g SO2
✕
= 1.17 mole SO2
a. 25.0 g Ca
✕
1 mole SO2
64.1 g SO2
1 mole Ca
40.1 g Ca
b. 5.00 g S
✕
1 mole S
32.1 g S
= 0.156 mole S
c. 40.0 g H2O
✕
1 mole H2O
18.0 g H2O
= 2.22 mole H2O
d. 100.0 g O2
✕
1 mole O2
32.00 g O2
= 3.125 mole O2 (Use atomic mass to 4 sig figs)
a. 25.0 g CO2 ✕
1 mole CO2
44.0 g CO2
= 0.568 mole CO2
b. 25.0 g Al(OH)3 ✕
1 mole Al(OH)3 = 0.321 mole Al(OH)3
78.0 g Al(OH)3
a. 50.0 g Ag
✕ 1 mole MgCl2
95.3 g MgCl2
c. 25.0 g MgCl2
7.22
a. 4.00 g NH3
✕
1 mole NH3
17.0 g NH3
= 0.623 mole Ca
= 0.262 mole MgCl2
= 0.235 mole NH3
b. 4.00 g Ca(NO3)2 ✕ 1 mole Ca(NO3)2 = 0.0244 mole Ca(NO3)2
164.1 g Ca(NO3)2
c. 4.00 g SO3
✕
1 mole SO3
80.1 g SO3
= 0.0499 mole SO3
7.23
480 g NaOH
✕
1 mole NaOH
40.0 g NaOH
= 12 mole NaOH
7.24
35.0 g Au
✕
1 mole Au
197.0 g Au
= 0.178 mole Au
✕
1 mole S
32.1 g S
= 0.78 moles of S
b. 125 g SO2
✕
1 mole SO2
64.1 g SO2
✕ 1 mole S
= 1.95 moles of S
1 mole SO2
c. 275 g Al2S3
✕
1 mole Al2S3
150.1 g Al2S3
✕ 3 moles S
= 5.50 moles of S
1 mole Al2S3
7.25 a. 25 g S
Chapter 7 Answers and Solutions
7.26
✕
a. 75 g C
1 mole C
12.0 g C
= 6.3 moles C
b. 0.25 mole C2H6 ✕ 2 mole C
= 0.50 mole of C
1 mole C2H6
c. 5.0 x 1024 CO2 molecules
=
7.27
✕ 1 mole CO2 molecules
6.02 x 1023 CO2 molecules
✕ 1 mole C atoms
1 mole CO2 molecules
8.3 mole C atoms
a. 40.0 g N ✕ 1 mole N
14.0 g N
✕ 6.02 x 1023 atoms of N = 1.7 ✕ 1024 atoms of N
1 mole N
b. 1.5 moles N2O4 ✕ 2 mole N
✕ 6.02 x 1023 atoms of N = 1.8 ✕1024 atoms of N
1 mole N2O4
1 mole N
c. 2.0 moles N2 ✕ 2 mole N
1 mole N2
7.28
✕ 6.02 x 1023 atoms of N = 2.4 ✕ 1024 atoms of N
1 mole N
a. 5.0 g Ag atoms ✕ 1 mole Ag atoms
107.9 g Ag atoms
✕ 6.02 x 1023 Ag atoms = 2.8 ✕ 1022 Ag Atoms
1 mole Ag atoms
b. 0.40 mole Ag2S ✕ 6.02 x 1023 Ag2S
1 mole Ag2S
✕ 2 Ag atoms
1 Ag2S
= 4.8 ✕ 1023 Ag Atoms
c. 0.75 g AgCl ✕ 1 mole AgCl ✕ 6.02 x 1023 AgCl units ✕ 1 Ag ion
= 3.2 ✕1021 ions
143.4 g AgCl
1 mole AgCl units
1 AgCl unit
7.29
a. 24.3 g Mg ✕
62.3 g MgF2
100 = 39.0% Mg
b. 40.1 g Ca
✕ 100 = 54.1% Ca
74.1 g Ca(OH)2
38.0 g F
62.3 g MgF2
✕ 100 = 61.0% F
32.0 g O
✕ 100 = 43.2%O
74.1 g Ca(OH)2
2.0 g H
✕ 100 = 2.7% H
74.1 g Ca(OH)2
c. 48.0 g C
✕ 100 = 40.0% C
120.0 g C4H8O4
8.0 g H
✕ 100
120.0 g C4H8O4
64.0 g O
✕ 100 = 53.3% O
120.0 g C4H8O4
✕ 100
= 22.6% S
b. 96.3 g S
150.3 g Al2S3
✕ 100
= 64.1% S
c. 32.1 g S
80.1 g SO3
✕ 100
= 40.1% S
7.30 a. 32.1 g S
142.1 g Na2SO4
✕
1 mole N =
14.0 g N
0.23 mole N
1.8 g O ✕
1 mole O =
16.0 g O
0.11 mole O
7.31 a. 3.2 g N
0.23 mole N
0.11 mole O
÷
÷
0.11 mole = 2.1 moles N
0.11 mole = 1.0 mole O
formula = N2O
= 6.7%H
Chemical Quantities
b. 8.0 g C ✕ 1 mole C =
12.0 g C
0.67 mole C
2.0 g H ✕ 1 mole H =
1.0 g H
2.0 moles H
2.0 moles H
0.67 mole C
÷
÷
0.67 mole = 3.0 moles H
0.67 mole = 1.0 mole C
c. 1.6 g H x
1 mole H =
1.0 g H
1.6 moles H
22. g N x
1 mole N =
14.0 g N
1.6 moles N
76 g O x
1 mole O =
16.0 g O
4.8 moles O
1.6 moles H
1.6 moles N
4.8 moles O
7.32 a. 2.9 g Ag
÷
÷
÷
1.6 moles
1.6 moles
1.6 moles
✕ 1 mole Ag
107.9 g Ag
0.43 g S ✕ 1 mole S
32.1 g S
= 1.0 mole H
= 1.0 mole N
= 3.0 mole O
= 0.013 mole S
b. 22 g Na ✕ 1 mole Na
23.0 g Na
= 0.96 mole Na
7.7 g O ✕ 1 mole O
16.0 g O
= 0.48 moles O
0.96 moles Na ÷ 0.48 mole = 2.0 moles Na
0.48 mole O ÷ 0.48 mole = 1.0 mole O
x 1 mole Na
23.0 g Na
= 0.83 mole Na
0.83 g H
x 1 mole H
1.0 g H
= 0.83 mole H
27 g S
x 1 mole S
32.1 g S
= 0.84 mole S
53 g O x
1 mole O =
16.0 g O
0.83 mole Na ÷
0.83 mole H ÷
0.83 mole S ÷
3.3 moles O ÷
0.83 moles
0.83 moles
0.83 moles
0.83 moles
formula = HNO3
= 0.027 mole Ag
0.027 mole Ag ÷ 0.013 mole = 2.1 moles Ag
0.013 mole S ÷ 0. 013 mole = 1.0 mole S
c. 19 g Na
formula = CH3
formula = Ag2S
formula = Na2O
3.3 moles O
= 1.0 mole Na
= 1.0 mole H
= 1.0 mole S
= 4.0 mole O
formula = NaHSO4
Chapter 7 Answers and Solutions
7.33 a. Converting from % by mass to grams in a100 g sample gives 71 g K and 29 g S
71 g K
✕
1 mole K =
39.1 g K
1.8 moles K
29 g S
✕
1 mole S =
32.1 g S
0.90 moles S
1.8 moles K
0.90 mole S
÷
÷
0.90 mole = 2.0 moles K
0.90 mole = 1.0 mole S
formula = K2S
b. Converting from % by mass to grams in a100 g sample gives 55 g Ga and 45 g F
55 g Ga ✕ 1 mole Ga =
69.7 g Ga
45 g F ✕
0.79 mole Ga
2.4 moles F
1 mole F =
19.0 g F
÷
÷
0.79 mole Ga
2.4 moles F
0.79 mole = 1.0 mole Ga
0.79 mole = 3.0 moles F
formula = GaF3
c. Converting from % by mass to grams in a100 g sample gives 31 g B and 69 g O
31 g B ✕
1 mole B = 2.9 moles B
10.8 g B
69 g O ✕
1 mole O =
16.0 g O
4.3 moles O
2.9 mole B ÷ 2.9 mole = 1.0 mole B
x 2 = 2.0 moles B
4.3 moles O ÷ 2.9 mole = 1.5 moles O x 2 = 3.0 moles O
formula = B2O3
7.34 a. Converting from % by mass to grams in a100 g sample gives 56 g Ca and 44 g S
56 g Ca
✕ 1 mole Ca =
40.1 g Ca
44 g S
✕ 1 mole S =
32.1 g S
1.4 moles Ca
1.4 mole S
÷
÷
1.4 moles Ca
1.4 moles S
1.4 mole = 1.0 moles Ca
1.4 mole = 1.0 mole S
formula = CaS
b. Converting from % by mass to grams in a100 g sample gives 78 g Ba and 22 g F
78 g Ba
x
22 g F x
0.57 mole Ba
1.2 moles F
1 mole Ba =
137.3 g Ba
1 mole F =
19.0 g F
÷
÷
0.57 mole Ba
1.2 moles F
0.57 mole = 1.0 mole Ba
0.57 mole = 2.1 moles F
formula = BaF2
Chemical Quantities
c. Converting from % by mass to grams in a100 g sample gives 76 g Zn and 24 g P
76 g Zn ✕
1 mole Zn = 1.2 moles Zn
65.4 g Zn
24 g P ✕
1 mole P =
31.0 g P
1.2 moles Zn
0.77 mole P
÷
÷
0.77 mole P
0.77 mole = 1.55 moles Zn ✕ 2 = 3.1 moles Zn
0.77 mole = 1.0 moles P ✕ 2 = 2.0 moles P formula = Zn3P2
7.35
a. Two SO2 molecules react with one O2 molecule to produce two SO3 molecules.
Two moles of SO2 react with one mole of O2 to produce two moles of SO3.
b. Four P atoms react with five O2 molecules to produce two P2O5 molecules.
Four moles of P react with five moles of O2 to produce two moles of P2O5.
7.36
a. Two aluminum atoms react with three chlorine molecules to produce two formula units of
AlCl3. Two moles of Aluminum react with three moles of chlorine to produce two moles
of AlCl3.
b. Four HCl molecules react with one O2 molecule to produce two Cl2 molecules and two
H2O molecules. Four moles of HCl react with one mole of O2 to form two moles of Cl2 and
two moles of H2O.
7.37
a. Reactants:
Products:
b. Reactants:
Products:
7.38
a. Reactants:
Products:
b. Reactant:
Products:
7.39
2 moles of SO2 plus 1 mole of O2 =
2 moles (64.1 g/mole) + 1 mole (32.0 g/mole) = 160.2 g
2 moles of SO3 = 2 moles (80.1 g/mole) = 160.2 g
4 moles of P and 5 moles of O2 =
4 moles (31.0 g/mole) + 5 moles (32.0 g/mole) = 284 g
2 moles of P2O5 = 2 moles (142 g/mole) = 284 g
2 moles of Al and 6 moles of Cl =
54.0 g + 213 g = 267 g
2 moles of Al and 6 moles of Cl =
54.0 g + 213 g = 267 g
4 moles of H and 4 moles of Cl plus 2 moles of O =
4.0 g + 142.0 g + 32.0 g = 178.0 g
4 moles of Cl plus 4 moles of H and 2 moles of O =
142.0 g + 4.0 g + 32.0 g = 178.0 g
a. 2 mole SO2 and
1 mole O2
1 mole O2 and
2 mole SO3
1 mole O2
2 mole SO2
2 mole SO3
1 mole O2
2 mole SO2
2 mole SO3
and
2 mole SO3
2 mole SO2
b 4 mole P
and
5 mole O2
5 mole O2 and
2 mole P2O5
5 mole O2
4 mole P
2 mole P2O5
5 mole O2
4 mole P
2 mole P2O5
and
2 mole P2O5
4 mole P
Chapter 7 Answers and Solutions
7.40
a. 2 mole Al
3 mole Cl2
and
3 mole Cl2 and
2 mole AlCl3
7.41
7.43
and
2 mole AlCl3
2 mole Al
2 mole AlCl3
3 mole Cl2
1 mole O2
4 mole HCl
4 mole HCl
2 mole Cl2
and
2 mole Cl2
4 mole HCl
4 mole HCl and
2 mole H2O
2 mole H2O
4 mole HCl
1 mole O2
2 mole Cl2
and
2 mole Cl2
1 mole O2
1 mole O2 and
2 mole H2O
2 mole H2O
1 mole O2
2 mole Cl2
2 mole H2O
and
2 mole H2O
2 mole Cl2
a. 2.0 mole H2 ✕
1 mole O2
2 mole H2
= 1.0 mole O2
b. 5.0 mole O2 ✕
2 mole H2
1 mole O2
= 10. mole H2
2 mole H2O
1 mole O2
= 5.0 mole H2O
a. 1.0 mole N2 ✕
3 moles H2
1 mole N2
= 3.0 moles H2
b. 0.60 mole NH3 ✕
1 mole N2
2 moles NH3
= 0.30 mole N2
c. 1.4 moles H2 ✕
2 moles NH3
3 mole H2
= 0.93 mole NH3
✕
a. 0.500 mole SO2 ✕ 5 mole C
2 mole SO2
= 1.25 mole C
✕
4 mole CO
5 mole C
= 0.96 mole CO
c. 0.50 mole CS2 ✕
2 mole SO2
1 mole CS2
= 1.0 mole SO2
✕
1 mole CS2
5 mole C
= 0.50 mole CS2
a. 2.00 mole C2H2 ✕
5 mole O2
2 mole C2H2
= 5.00 mole O2
b. 3.5 mole C2H2 ✕
4 mole CO2
2 mole C2H2
= 7.0 mole CO2
c. 0.50 mole H2O ✕
2 mole C2H2
2 mole H2O
= 0.50 mole C2H2
d. 0.100 mole O2 ✕
4 mole CO2
5 mole O2
= 0.080 mole CO2
b. 1.2 mole C
d. 2.5 mole C
7.44
2 mole Al
2 mole AlCl3
b. 4 mole HCl and
1 mole O2
c. 2.5 mole O2
7.42
3 mole Cl2
2 mole Al
Chemical Quantities
7.45
7.46
7.47
a. 2.5 mole Na ✕
2 mole Na2O ✕ 62.0 g Na2O
4 mole Na
1 mole Na2O
= 78 g Na2O
b. 18.0 g Na
✕
1 mole Na
23.0 g Na
c. 75.0 g Na2O
✕
1 mole Na2O ✕ 1 mole O2 ✕ 32.0 g O2
62.0 g Na2O
2 mole Na2O 1 mole O2
a. 1.8 mole H2 ✕
✕ 1 mole O2 ✕ 32.0 g O2
4 mole Na
1 mole O2
2 mole NH3
3 mole H2
✕ 17.0 g NH3
1 mole NH3
= 20. g NH3
✕
1 mole N2
28.0 g N2
✕ 3 mole H2
1 mole N2
c. 12 g H2
✕
1 mole H2
2.0 g H2
✕ 2 mole NH3 ✕ 17.0 g NH3 = 68 g NH3
3 mole H2
1 mole NH3
3 mole O2
4 mole NH3
✕ 32.0 g O2
1 mole O2
1 mole O2
32.0 g O2
✕ 2 mole N2 ✕ 28.0 g N2
3 mole O2
1 mole N2
a. 8.0 mole NH3 ✕
✕
✕ 2.0 g H2
1 mole H2
a. 2.50 mole Fe2O3 ✕ 3 mole C
✕
1 mole Fe2O3
b. 36.0 g C
c. 6.00 g Fe2O3
a. 40.0 g C
✕
1 mole C
12.0 g C
✕ 1 mole Fe2O3 ✕
159.8 g Fe2O3
✕
1 mole C
12.0 g C
✕
= 0.60 g H2
= 190 g O2
c. 34 g NH3 ✕ 1 mole NH3 ✕ 6 mole H2O ✕ 18.0 g H2O
17.0 g NH3
4 mole NH3
1 mole H2O
7.49
= 19.4 g O2
b. 2.80 g N2
b. 6.50 g O2
7.48
= 6.26 g O2
12.0 g C
1 mole C
✕ 3 mole CO ✕ 28.0 g CO
3 mole C
1 mole CO
= 3.79 g N2
= 54 g H2O
= 90.0 g C
= 84.0 g CO
2 mole Fe
✕ 55.9 g Fe
1 mole Fe2O3
1 mole Fe
= 4.20 g Fe
1mole CS2 ✕ 76.2 g CS2
5 moles C
1 mole CS2
= 50.8 g CS2
36.0 g CS2 (actual)
✕ 100 = 70.9%
50.8 g CS2(theoretical)
b. 32.0 g SO2 ✕ 1 mole SO2 ✕
64.1 g SO2
1mole CS2 ✕ 76.2 g CS2
2 moles SO2
1 mole CS2
= 19.0 g CS2
12.0 g CS2 (actual)
✕ 100 = 63.1%
19.0 g CS2(theoretical)
7.50 a. Theorectical yield of Fe:
65.0 g Fe2O3 ✕ 1 mole Fe2O3 ✕ 2 mole Fe
✕ 55.9 g Fe
159.8 g Fe2O3= 1 mole Fe2O3
1 mole Fe
Percent yield:
15.0 g Fe (actual)
✕ 100 = 33.0 % Fe actually produced
45.5 g Fe(theoretical)
= 45.5 Fe
Chapter 7 Answers and Solutions
b. Theorectical yield of CO2:
75.0 g CO ✕ 1 mole CO ✕ 3 mole CO2 ✕ 44.0 g CO2
28.0 g CO
3 moles CO
1 mole CO2
Percent yield:
✕ 100 = 12.7 % CO2 actually produced
15.0 g CO2 (actual)
118.0 g CO2(theoretical)
7.51
7.52
50.0 g Al ✕
1 mole Al
27.0 g Al
✕ 2 moles Al2O3 ✕ 102.0 g Al2O3
4 moles Al
1 mole Al2O3
= 118 g CO2
= 94.4 g Al2O3
Use the percent yield to convert theoretical to actual:
70.8g Al2O3 (actual)
94.4 g Al2O3 x 75.0 g Al2O3 =
100 g Al2O3
Theorectical yield of CO2:
45.0 g C3H8 ✕ 1 mole C3H8 ✕ 3 moles CO3 ✕ 44.0 g CO3 = 135 g CO2
44.0 g C3H8
1 moles C3H8
1 mole CO3
Use the percent yield to convert theoretical to actual:
135 g CO2 x 60.0 g CO2 = 81.0 g CO2 (actual)
100 g CO2
7.53
7.54
In the expression for Keq the products are divided by the reactants with each concentration raised
to a power that equals the coefficient in the equation:
b. Keq =[N2][O2]
a. Keq = [CS2][H2]4
[CH4][H2S]2
[NO]2
c. Keq = [CS2][O2]4
[SO3]2[CO2]
In the expression for Keq the products are divided by the reactants with each concentration raised
to a power that equals the coefficient in the equation:
b. Keq = [CH3OH]
a. Keq = [H2][Br2]
[HBr]2
[CO][H2]2
c. Keq = [CS2][H2]4
[H2S]2[CH4]
7.55
a. A large Keq means that the products are favored.
b. A small Keq means that the reactants are favored.
7.56
a. A small Keq means that the reactants are favored.
b. A large Keq means that the products are favored.
7.57
a. 78.2 g K
194.2 g K2CrO4
✕ 100 = 40.3% K
64.0 g O
194.2 g K2CrO4
✕ 100 = 33.7% O
b. 27.0 g Al
✕ 100 = 12.9% Al
210.0 g Al(HCO3)3
36.0 g C
✕ 100 = 17.1% C
210.0 g Al(HCO3)3
x 100 = 26.8 %Cr
52.0g Cr
194.2 g K2CrO4
3.0g H
✕ 100 = 1.4 %H
210.0 g Al(HCO3)3
144.0 g O
✕ 100 = 68.6% O
210.0 g Al(HCO3)3
Chemical Quantities
7.58
7.59
c. 72.0 g C
180.0 g C6H12O6
✕ 100 = 40.0% C
96.0 g O
180.0 g C6H12O6
✕ 100 = 53.3% O
a. 124.0 g P
284 g P4O10
✕ 100 = 43.7 % P
b. 62.0 g P
134.9 g Mg3P2
✕ 100 = 46.0 % P
c. 62.0 g P
310.3 g Ca3(PO4)2
✕ 100 = 20.0 % P
12.0g H
✕ 100 = 6.7 %H
180.0 g C6H12O6
a. 2.20 g S
✕
1 mole S =
32.1 g S
0.0685 mole S
7.81 g F
✕
1 mole F =
19.0 g F
0.411 mole F
0.0685 mole S
0.411 moles F
÷
÷
0.0685 mole = 1.00 mole S
0.0685 mole = 6.00 moles F
b. 6.35 g Ag
✕
1 mole Ag =
107.9 g Ag
0.0589 mole Ag
0.825 g N
✕
1 mole N =
14.0 g N
0.0589 mole N
2.83 g O
✕
1 mole O =
16.0 g O
0.177 mole O
0.0589 mole Ag ÷ 0.0589 mole = 1.00 mole Ag
0.0589 mole N ÷ 0.0589 mole = 1.00 mole N
0.177 moles O ÷ 0.0589 mole = 3.00 moles O
formula = SF6
formula = AgNO3
c. 89.2 g Au ✕ 1 mole Au = 0.453 mole Au
197.0 g Au
10.9 g O ✕
0.453 mole Au
0.681 moles O
7.60
a. 61 g Sn
1 mole O = 0.681 mole O
16.0 g O
÷ 0.453 mole
÷ 0.453 mole
✕ 1 mole Sn =
118.7 g Sn
39 g F ✕ 1 mole F =
19.0 g F
= 1.00 mole Au x 2 = 2.00 moles Au
= 1.50 moles O x 2 = 3.00 mole O formula = Au2O3
0.51 mole Sn
2.1 moles F
0.51 mole Sn ÷ 0.51 mole = 1.0 mole Sn
2.1 moles F ÷ 0.51 mole = 4.1 moles F
formula = SnF4
Chapter 7 Answers and Solutions
b. 25.9 g N
74.1 g O
✕
1 mole N =
14.0 g N
1.85 moles N
✕
1 mole O =
16.0 g O
4.63 moles O
÷
÷
1.85 moles N
4.63 moles O
1.85 mole = 1.00 mole N
1.85 mole = 2.50 moles O
Calculation of whole numbers
1.00 mole N ✕ 2
= 2.00 mole N
2.50 moles O ✕ 2
= 5.00 moles O
Formula N2O5
✕
1 mole Al =
27.0 g Al
0.819 mole Al
25.4 g P
✕
1 mole P =
31.0 g P
0.819 mole P
52.5 g O
✕
1 mole O =
16.0 g O
3.28 moles O
c. 22.1 g Al
0.819 mole Al
0.819 moles P
4.00 moles O
÷ 0.819 mole
÷ 0.819 mole
÷ 0.819 mole
= 1.00 mole Al
= 1.00 moles O
= 4.00 mole O formula = AlPO4
7.61
70.0 kg body wt
✕ 60.0 kg H2O ✕ 1000 g ✕ 1 mole H2O = 2.33 x 103 moles H2O
100 kg body wt 1 kg
18.0 g H2O
7.62
10.0 mL blood
✕ 400. mg C2H6O ✕ 1 g
✕ 1 mole C2H6O = 8.70 ✕ 10−4 mole C2H6O
100 mL blood
1000 mg 46.0 g C2H6O
7.63
a. 124 g C2H6O ✕ 1 mole C2H6O ✕ 1 mole C6H12O6
46.0 g C2H6O
2 mole C2H6O
= 1.35 mole C6H12O6
b. 0.240 kg C6H12O6 ✕ 1000 g ✕ 1 mole C6H12O6 ✕ 2 mole C2H6O ✕ 46.0 g C2H6O
1 kg
180.0 g C6H12O6
1 mole C6H12O6 1 mole C2H6O
= 123 g C2H6O
7.64
a. C2H6O + 3O2 → 2CO2 + 3H2O
b. 4.0 mole C2H6O ✕ 3 mole O2
1 mole C2H6O
c. 88 g CO2
✕
1 mole CO2
44.0 g CO2
= 12 mole O2
✕
3 mole O2
2 mole CO2
✕ 32.0 g O2
1 mole O2
= 96 g O2
d. 125 g C2H6O ✕
1 mole C2H6O ✕
46.0 g C2H6O
2 mole CO2 ✕ 44.0 g CO2
1 mole C2H6O 1 mole CO2
= 239 g CO2
125 g C2H6O ✕
1 mole C2H6O ✕
46.0 g C2H6O
3 mole H2O ✕ 18.0 g H2O
1 mole C2H6O
1 mole H2O
= 147 g
Chemical Quantities
7.65
2NH3 + 5F2 → N2F4 + 6HF
a. 4.00 mole HF ✕
✕
4.00 mole HF
b. 1.50 mole NH3 ✕
2 mole NH3
6 mole HF
= 1.33 mole NH3
5 mole F2
6 mole HF
= 3.33 mole F2
5 mole F2
2 mole NH3
✕ 38.0 g F2
1 mole F2
c. 3.40 g NH3 ✕ 1 mole NH3
17.0 g NH3
✕
1 mole N2F4
2 mole NH3
= 143 g F2
✕ 104.0 g N2F4 = 10.4 g N2F4
1 mole N2F4
7.66 Theoretical yield
50.0 g Fe2O3
✕
Percent yield
32.8 g Fe x 100
35.0
7.67
C2H2 (g) + 3O2(g)
1 mole Fe2O3 ✕
159.8 g Fe2O3
2 moles Fe ✕
1 mole Fe2O3
55.9 g Fe
1 mole Fe
= 35.0 g Fe
= 93.7 % Fe (actual yield)
→ 2CO2(g) + H2O(g)
22.5 g C2H2 ✕ 1 mole C2H2 ✕ 2 moles CO2 ✕ 44.0 g CO2 = 76.2 g CO2 (theoretical)
26.0 g C2H2
1 mole C2H2
1 mole CO2
62.0 g (actual)
✕ 100
76.2 g (theoretical)
= 81.4% (percent yield)
7.68 Theoretical yield would be
30.0 g NH3 ✕ 100.0 g NH3 = 46.2 g NH3
65.0 %
46.2 g NH3 ✕ 1 mole NH3 ✕ 1 mole N2
✕ 28.0 g N2 = 38.0 g N2 reacted
17.0 g NH3
2 moles NH3
1 mole N2