Dr. Zellmer
Chemistry 122
Wednesday 10:30 AM
Time: 23 mins
Summer Quarter 2008
June 25, 2008
Quiz I
Name
KEY
Rec. Instr.
10:30
----------------------------------------------------------------------------------------------------------------------------------------
2
1.
(5 pts)
A sample of N gas occupies 10.00 L at 25°C and a pressure of 14.51 lb/in .
At what
2
2
temperature
(in
°C
) will it occupy 20.00 L at a pressure of 0.9211 atm?
(Mol. Wt.: N = 28.02)
(1 atm = 101.325 kPa = 14.7 lb/in = 760 torr = 760 mm Hg)
2
Since P, V & T all change use the Combined Gas Law:
2
2
1
1
P V
P V
-------
=
-------
T
MUST
be in
kelvin
2
1
T
T
1
1
1
P = 14.51 lb/in
V
= 10.00 L
T
= 25°C + 273.15 = 29
8
.15 K
2
14.7 lb/in
2
2
2
2
P = 0.9211 atm × ------------
= 13.5
4
0 lb/in
V
= 20.00 L
T
= ?
2
1atm
2
2
1
2
2
P V T
P
V
13.5
4
0 lb/in
20.00 L
2
2
1
T
=
----------
=
(-----)(-----)T
= (----------------)(-----------) 29
8
.15 K
= 55
6
.44 K
=
28
3
.29°C
1
1
1
1
P V
P
V
14.51 lb/in
10.00 L
2
=
283°C
(3 s.f.)
2.
(7 pts) A gas with a molecular weight of 40.0 amu has a mass of 5.35 g at STP in a container of
unknown volume.
What is the
volume
(in L) of the container?
STP
=> Standard Temp. & Pressure:
T = 0°C (273.15K)
&
P = 1 atm
To calculate the volume you need moles.
You can get this from the molecular weight or molar
mass,
M
,
m
mass
m
M
= ---- = ---------
or
n = -----
(or use dimensional analysis)
n
moles
M
m
5.35 g
1 mol
n
=
----
=
---------------
or
? mol = 5.35 g x --------- = 0.13
3
75 mol
M
40.0 g/mol
40.0 g
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- Summer '07
- Zellmer
- Chemistry
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