Chemistry 114
Second Hour Exam
Name:____________
1. (8 points) Identify the dominant intermolecular force present in particles of the following solids
NH4Cl
C2H6
NH3
N2
2. (12 points) In each of the following groups of substances pick the one that has the given
property. Justify your answer
Highest boiling point: N2 , O2, NO
Lowest Freezing point H2O, NaCl, HF
Strongest hydrogen bonding: NH3, PH3, SbH3
Greatest viscosity: CH3CH2CH2CH3, CH3CH2OH, HOCH2CH2OH
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3. (10 points) In the Germanium crystal there is a 3.265 D distance between atoms. What angle
will the first order (n=1) diffraction line be for 1.54 D wavelength X-rays
4. (10 points) What types of solids will each of the following substances form
CO
Ru
KBr
C
P4
5. (10 points) The vapor pressure of water is 525.8 torr at 90oC and 760 torr at 100oC. What is
the )Hvap for water?
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6. (10 points) I have a substance that at 1 atm of pressure melts at -20oC and boils at 40oC. When
you have the same substance at 0.1 atm the material sublimes at -10oC. Make a reasonable phase
diagram for this compound. On your phase diagram note the location of the triple point and the
critical point.
7. (10 points) I have a solution that is 5% by weight acetic acid. What is the molality of this
solution? (MW acetic acid = 60.052)
8. (10 points) What is the boiling point of the 5% acetic acid solution that you calculated molality
for in problem 7? (Kb water = 0.51 oC@kg/mol)
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9. A (5 points) The vapor pressure of dimethyl ether (CH3OCH3) is 623 tor at 300oC. The vapor
pressure of methanol is 18.7 tor at this same temperature. If I mix 1 mole of dimethyl ether with
3 moles of methanol, what is the vapor pressure of a mixture?
B(5 points) Say I noticed that the above solution got hotter when I mixed it together,
would you expect your answer in A to be higher or lower? Why?
10. (10 points)What is a colloid?
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