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Name:_______________________________
Student Number:______________________________
CHM2132 Quiz 4
1. On a cold, dry morning after a frost the temperature was 5
o
C and the partial pressure of water in
the atmosphere was 0.20 kPa.
Will the frost sublime?
What partial pressure of water would ensure
that the frost remained? You must show your work. (5 marks)
1
016
.
44
−
=
Δ
kJmol
H
m
vap
1
008
.
6
−
=
Δ
kJmol
H
m
fus
T
Triple Point
= 273.15 K
p
Triple point
=0.006 atm = 607.95 Pa
ln
p
2
p
1
⎛
⎝
⎜
⎞
⎠
⎟
=−
Δ
vap
H
m
R
1
T
2
−
1
T
1
⎛
⎝
⎜
⎞
⎠
⎟
Δ
sub
H
m
=Δ
vap
H
m
+Δ
fus
H
m
=
44.016 kJ mol
1
+ 6.008 kJ mol
1
=
50.024 kJ mol
1
Since
T
Triple Point
= 273.15 K and
p
Triple point
=0.006 atm
ln
p
2
Δ
vap
H
m
R
1
T
2
−
1
T
1
⎛
⎝
⎜
⎞
⎠
⎟
+
ln
p
1
=
−
50024 J mol
1
8.314 J K
1
mol
1
1
273  5
()
K
−
1
273.15 K
⎛
⎝
⎜
⎞
⎠
⎟
+
ln 0.006
=
2.16
p
2
=
0.0039 atm=0.4 kPa
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