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Version 096 – Exam 1 – Fakhreddine – (52395) 1
This print-out should have 25 questions.
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before answering.
001 12.0 points
specific heat of H2O(l) = 4.18 J/g.C, enthalpy
of evaporation of water = 2.26 x 103 J/g; spe-
cific heat of H2O (g) = 2.03 J/g.C; enthalpy
of fusion of ice = 334.0 J/g; and specific heat
of H2O(s) = 2.09 J/g.C
Consider an insulated system containing
150 g of liquid water and 150 g of ice at
equilibrium under atmospheric pressure. A
total of 17 g of steam at 110
◦
C is admitted to
the system. What is the phase composition
and temperature when equilibrium is reestab-
lished?
1. 300 g of water and 17 g of ice at 0
◦
C
2. 317 g of water at 3.2
◦
C
3. 317 g of water at 6.8
◦
C
4. 304 g of water and 13 g of ice at 0
◦
C
correct
5. 310 g of water and 7 g of ice at 0
◦
C
6. 317 g of water at 15.3
◦
C
1. None of these is correct.
2. strong binding in the solid and weak
solvent-solute interaction.
Explanation:
002 12.0 points
How many grams of methanol (CH
3
OH)
are needed to lower the freezing point of
400 mL of water by 2.5
◦
C? ( K
f
water =
1 . 86
◦
C/molality)
1. 9.71
2. 17.2 correct
3. 12.8
4. 21.8
5. 18.3
Explanation:
K
f H
2
O
= 1 . 86
◦
C /m V
water
= 400 L
FP depression = 2.5
◦
C
Δ T
f
= K
f
· m
m =
Δ T
f
K
f
=
2 . 5
◦
C
1 . 86
◦
C /m
= 1 . 344 m
m
H
2
O
= 400 mL ×
1 . 00 g
mL
×
10
− 3
kg
g
= 0 . 4 kg H
2
O
m =
n
CH
3
OH
kg water
=
g CH
3
OH
MW
CH
3
OH
kg water
g CH
3
OH = m (kg water) (MW
CH
3
OH
)
=
parenleftbigg
1 . 344 mol CH
3
OH
kg water
parenrightbigg
× (0 . 400 kg water)
×
parenleftbigg
32 . 0 g CH
3
OH
mol CH
3
OH
parenrightbigg
= 17 . 2 g CH
3
OH
003 5.0 points
Dissociation of a solid is aided by
3. strong interaction between solvent
molecules.
4. weak binding of species in the solid and
strong interactions between the solvent and
solute. correct
Explanation:
Weak intermolecular forces in the solute
facilitate separation of its particles and strong
attractive forces between solute and solvent
facilitate dissociation of a solid.
004 12.0 points
Methanol (CH
3
OH) and ethanol (C
2
H
5
OH)
are common organic solvents. The vapor
pressures of pure methanol and pure ethanol

Version 096 – Exam 1 – Fakhreddine – (52395) 2
at 25
◦
C are 122 . 7 torr and 58 . 9 torr, respec-
tively. If the mole fraction of CH
3
OH in the
mixture of the two solvents at 25
◦
C is 0 . 2,
what is the mole fraction of C
2
H
5
OH in the
vapor phase that is in equilibrium with the
liquid mixture?