(Reference: Chang 5.30)
4.
A sample of nitrogen gas kept in a container of volume 2.3 L and at a temperature of
32°C exerts a pressure 4.7 atm. Calculate the number of moles of gas present.
(8
points)
V=2.3L T=32°C= (32+273)K= 305K
P=4.7atm
R=.0821Latm/K mol
n
=
PV
RT
→
4.7
(
2.3
)
.0821
(
305
)
→
10.81
25.0405
→n
=
.43
mol
(Reference: Chang 5.31)
5.
What volume will 5.6 moles of sulfur hexafluoride (SF
6
) gas occupy if the
temperature and pressure of the gas are 128°C and 9.4 atm?
(8 points)
n=5.6mol
T=128°C=(128+273)= 401K
P=9.4atm R= .0821L
V
=
nRT
P
→
5.6
(
.0821
)
(
401
)
9.4
→
184.36
9.4
→
19.6123
→V
=
20
L
(Reference: Chang 5.33)
6.
A gas-filled balloon having a volume of 2.50 L at 1.2 atm and 25°C is allowed to rise
to the stratosphere (about 30 km above the surface of Earth), where the temperature
and pressure are –23°C and 3.00 × 10
–3
atm, respectively. Calculate the final volume
of the balloon.
(8 points)
P
1
V
1
T
1
=
P
2
V
2
T
2
→
1.2
(
2.5
)
298.15
→
3.00
∗
10
−
3
(
V
2
)
250.15
→
3
298.15
=
3.00
∗
10
−
3
(
V
2
)
250.15
→
→
.0101
=
3.00
∗
10
−
3
(
V
2
)
250.15
→
2.527
=
3.00
∗
10
−
3
(
V
2
)
→
839
L
(Reference: Chang 5.35)
7.
A 2.10-L vessel contains 4.65 g of a gas at 1.00 atm and 27.0°C. (a) Calculate the
density of the gas in grams per liter. (b) What is the molar mass of the gas?
(10
points)
A)V=2.1L
Mass=4.65g
D
=
m
v
→
4.65
2.10
=
2.214
g
/
L
B) V=2.1L
P= 1atm m=4.65g T=27.0°C= (27+273)= 300K
2
Copyright © 2017 by Thomas Edison State
University
. All rights reserved.

4.65
g
(
.0821
L
)(
300
K
)
1
atm
(
2.10
L
)
→
114.5295
2.10

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