segal (mas6582) – H10: Gases 2 – mccord – (50970)
1
This
printout
should
have
22
questions.
Multiplechoice questions may continue on
the next column or page – find all choices
before answering.
001
10.0 points
What is the mass of oxygen gas in a 14.7 L
container at 22.0
◦
C and 6.70 atm?
Correct answer: 130
.
13 g.
Explanation:
T
= 22
.
0
◦
C + 273 = 295 K
P
= 6
.
7 atm
V
= 14
.
7 L
m = ?
n
=
P V
R T
=
(6
.
7 atm)(14
.
7 L)
(
0
.
0821
L
·
atm
mol
·
K
)
(295 K)
= 4
.
06656 mol O
2
m = (4
.
06656 mol)
parenleftbigg
32 g
mol
parenrightbigg
= 130
.
13 g O
2
002
10.0 points
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 75.9 g toluene and 62.0 g benzene.
Correct answer: 0
.
509.
Explanation:
m
toluene
= 75.9 g
m
benzene
= 62.0 g
n
toulene
= (75
.
9 g toluene)
parenleftBig
1 mol
92
.
14 g
parenrightBig
= 0
.
824 mol
n
benzene
= (62
.
0 g benzene)
parenleftBig
1 mol
78
.
11 g
parenrightBig
= 0
.
794 mol
The total number of moles of all species
present is
0
.
824 mol + 0
.
794 mol = 1
.
62 mol
The mole fraction of toluene is then
X
toluene
=
n
toluene
n
total
=
0
.
824 mol
1
.
62 mol
= 0
.
509
003 (part 1 of 4) 10.0 points
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 78 L of oxygen
at 3
.
17 atm and 145
◦
C with an excess of iron
pyrite?
Correct answer: 209
.
294 g.
Explanation:
P
= 3
.
17 atm
T
= 145
◦
C + 273 = 418 K
R
= 0
.
08206
L
·
atm
K
·
mol
V
= 78 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
=
(3
.
17 atm) (78 L)
(
0
.
08206
L
·
atm
K
·
mol
)
(418 K)
= 7
.
20852 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
(7
.
20852 mol O
2
)
= 209
.
294 g Fe
2
O
3
.
004 (part 2 of 4) 10.0 points
If the sulfur dioxide that is generated above
is dissolved to form 3 L of aqueous solution,
what is the molar concentration of the result
ing sulfurous acid (H
2
SO
3
) solution?
Correct answer: 1
.
74752 M.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
segal (mas6582) – H10: Gases 2 – mccord – (50970)
2
Explanation:
V
= 3 L
SO
2
(g) + H
2
O(
ℓ
)
→
H
2
SO
3
(aq)
.
From the stoichiometry,
n
SO
2
= (7
.
20852 mol)
parenleftbigg
8
n
SO
2
11
n
O
2
parenrightbigg
= 5
.
24256 mol
.
5
.
24256 mol of SO
2
will dissolve in 3 L of
water to form a solution that is
5
.
24256 mol
3 L
= 1
.
74752 M in H
2
SO
4
.
005 (part 3 of 4) 10.0 points
What mass of SO
2
is produced in the burning
of 1 tonne (1 t = 1000 kg) of highsulfur coal,
if the coal is 6% pyrite by mass?
Correct answer: 64
.
0771 kg.
Explanation:
m
coal
= 1000 kg
m
FeS
2
= 6%(1000 kg) = 60 kg = 60000 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
60000 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
= 64077
.
1 g = 64
.
0771 kg SO
2
.
This is the end of the preview.
Sign up
to
access the rest of the document.
 Fall '08
 wandelt
 Chemistry, mol

Click to edit the document details