Chem 110, 2002 Scantron form
1. The enthalpy (heat) of vaporization for ethanol (C2H5OH) is 43.3 kJ/mol. How much heat, in kilojoules, is required to vaporize 230 g of ethanol at 25°C? (F.W. of ethanol = 46.06)
a. 9.96 x 103 b. 5.00 c. 108 d. 216 e. 245
2. When the pressure over a liquid is decreased, the boiling point of the liquid will
a. always increase.
b. always decrease.
c. increase or decrease.
d. remain unchanged.
3. Consider a closed container containing a liquid and its vapor. Which statement is incorrect?
a. The vapor exerts a pressure called the vapor pressure.
b. Increasing the temperature of the liquid would lead to a greater vapor pressure.
c. The vapor pressure is independent of the size of the container
d. Evaporation and condensation will eventually cease after a constant pressure has been attained.
e. At equilibrium, the rate of evaporation is equal to the rate of condensation.
4. Which of the following statements about water is incorrect?
a. The boiling point is much higher than expected based on its formula weight.
b. There are strong intermolecular forces due to hydrogen bonding.
c. Solid (ice) is less dense than liquid (water).
d. The solid-liquid line in the phase diagram has an unusual negative slope.
e. Ice cannot sublime directly to vapor at any temperature.
5. How many of the following processes are endothermic?
freezing vaporization sublimation melting condensation
a. 1 b. 2 c. 3 d. 4 e. 5
6. In which substance would the dispersion forces be the strongest?
a. C(CH3)4 b. CH3CH2CH2CH2CH3 c. CH3CH2CH3 d. CH3CH3 e. CH4
7. Which of the following would involve hydrogen bonding as a significant intermolecular force?
a. HI b. c. d. e.
8. Consider the phase diagram for CO2. In going from point B to point C:
a. liquid CO2 becomes solid
b. gaseous CO2 becomes liquid
c. solid CO2 becomes liquid
d. solid CO2 becomes gaseous
e. liquid CO2 becomes gaseous