patel (ap28872) – H10: Gases 2 – mccord – (51600)
1
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22
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001
10.0points
What is the mass of oxygen gas in a 12.4 L
container at 14.0
◦
C and 6.84 atm?
Correct answer: 115
.
187 g.
Explanation:
T
= 14
.
0
◦
C + 273 = 287 K
P
= 6
.
84 atm
V
= 12
.
4 L
m = ?
n
=
P V
R T
=
(6
.
84 atm)(12
.
4 L)
(
0
.
0821
L
·
atm
mol
·
K
)
(287 K)
= 3
.
59959 mol O
2
m = (3
.
59959 mol)
parenleftbigg
32 g
mol
parenrightbigg
= 115
.
187 g O
2
002
10.0points
Toluene (C
6
H
5
CH
3
) is a liquid compound
similar to benzene (C
6
H
6
).
Calculate the
mole fraction of toluene in the solution that
contains 111 g toluene and 82.0 g benzene.
Correct answer: 0
.
534.
Explanation:
m
toluene
= 111 g
m
benzene
= 82.0 g
n
toulene
= (111 g toluene)
parenleftBig
1 mol
92
.
14 g
parenrightBig
= 1
.
20 mol
n
benzene
= (82
.
0 g benzene)
parenleftBig
1 mol
78
.
11 g
parenrightBig
= 1
.
05 mol
The total number of moles of all species
present is
1
.
20 mol + 1
.
05 mol = 2
.
25 mol
The mole fraction of toluene is then
X
toluene
=
n
toluene
n
total
=
1
.
20 mol
2
.
25 mol
= 0
.
534
003(part1of4)10.0points
Iron pyrite (FeS
2
) is the form in which much of
the sulfur exists in coal. In the combustion of
coal, oxygen reacts with iron pyrite to produce
iron(III) oxide and sulfur dioxide, which is a
major source of air pollution and a substantial
contributor to acid rain. What mass of Fe
2
O
3
is produced from the reaction is 70 L of oxygen
at 4
.
14 atm and 145
◦
C with an excess of iron
pyrite?
Correct answer: 245
.
302 g.
Explanation:
P
= 4
.
14 atm
T
= 145
◦
C + 273 = 418 K
R
= 0
.
08206
L
·
atm
K
·
mol
V
= 70 L
MW
Fe
2
O
3
= 2(55
.
845 g
/
mol)
+ 3(15
.
9994 g
/
mol)
= 159
.
688 g
/
mol
The balanced equation is
4 FeS
2
(s) + 11 O
2
(g)
→
2 Fe
2
O
3
(s) + 8 SO
2
(g)
Applying the ideal gas law to the O
2
,
P V
=
n R T
n
=
P V
R T
=
(4
.
14 atm) (70 L)
(
0
.
08206
L
·
atm
K
·
mol
)
(418 K)
= 8
.
44871 mol
.
From stoichiometry and the molar mass of
Fe
2
O
3
,
m
Fe
2
O
3
= (159
.
688 g
/
mol Fe
2
O
3
)
×
2 mol Fe
2
O
3
11 mol O
2
(8
.
44871 mol O
2
)
= 245
.
302 g Fe
2
O
3
.
004(part2of4)10.0points
If the sulfur dioxide that is generated above
is dissolved to form 7
.
1 L of aqueous solu
tion, what is the molar concentration of the
resulting sulfurous acid (H
2
SO
3
) solution?
Correct answer: 0
.
865425 M.
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patel (ap28872) – H10: Gases 2 – mccord – (51600)
2
Explanation:
V
= 7
.
1 L
SO
2
(g) + H
2
O(
ℓ
)
→
H
2
SO
3
(aq)
.
From the stoichiometry,
n
SO
2
= (8
.
44871 mol)
parenleftbigg
8
n
SO
2
11
n
O
2
parenrightbigg
= 6
.
14452 mol
.
6
.
14452 mol of SO
2
will dissolve in 7
.
1 L of
water to form a solution that is
6
.
14452 mol
7
.
1 L
= 0
.
865425 M in H
2
SO
4
.
005(part3of4)10.0points
What mass of SO
2
is produced in the burning
of 1 tonne (1 t = 1000 kg) of highsulfur coal,
if the coal is 4% pyrite by mass?
Correct answer: 42
.
7181 kg.
Explanation:
m
coal
= 1000 kg
m
FeS
2
= 4%(1000 kg) = 40 kg = 40000 g
MW
FeS
2
= 55
.
845 g
/
mol + 2(32
.
065 g
/
mol)
= 119
.
975 g
MW
SO
2
= 32
.
065 g
/
mol + 2(15
.
9994 g
/
mol)
= 64
.
0638 g
m
SO
2
= 1000 kg coal
parenleftbigg
40000 g FeS
2
1000 kg coal
parenrightbigg
×
parenleftbigg
1 mol FeS
2
119
.
975 g FeS
2
parenrightbigg
×
parenleftbigg
8 mol SO
2
4 mol FeS
2
parenrightbigg parenleftbigg
64
.
0638 g SO
2
1 mol SO
2
parenrightbigg
= 42718
.
1 g = 42
.
7181 kg SO
2
.
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 Spring '07
 Fakhreddine/Lyon
 Chemistry, patel, mol

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