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Solutions for Exam 3 Form Code A Fall 2008
1.
MgCl
2
dissociates in water to produce 3 ions per formula unit, so 0.008 moles x 3 =
0.024 moles of ions.
MgCl
2
therefore has a larger colligative effect than the other
compounds.
(Answer 4)
2.
ln (760/P
2
) = (23,500 J/mol)/(8.314 J/mol•K)(1/223.15K – 1/239.75K)
ln (760/P
2
) = 0.877
e
0.877
= 2.40 = 760/P
2
so P
2
=
316 torr
(Answer 2)
3.
Particles with greater number of electrons and therefore larger electron clouds (i.e.,
larger particles) have a greater polarizability.
(Answer 1)
is the only option that lists the
larger, and therefore most polarizable, particle first
(Se
2
is larger and more polarizable
than S
2
).
4.
ΔT
f
= K
f
•
m
=
(1.99 °C/
m
)[(75 g / 106.1 g/mol) / (0.850 kg)] = 1.66°C
So 117.3°C – 1.66°C =
119.0°C
(Answer 3)
5.
(1000 g / 18.02 g/mol)(40.7 kJ/mol) = 2258 kJ released
(2258 kJ released) / (6.01 kJ/mol)(18.02 g/mol) =
6.77 kg melted (Answer 1)
6.
C = K
H
•P
=
(3.2x10
2
M/atm)(5.5 atm) =
0.18 M
(Answer 4)
7.
Vapor pressure depends ONLY on temperature and and not container volume), so
since the temperature did not change, the vapor pressure remained at
50 torr
(Answer 2)
8.
CCl
4
has a lower BP than CBr
4
due to its lower molecular mass
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This note was uploaded on 09/25/2011 for the course CHM 2046 taught by Professor Veige/martin during the Spring '07 term at University of Florida.
 Spring '07
 veige/martin
 Mole

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