Chapter 8:
Physical Equilibria
1. How is vapor pressure related to equilibrium?
a. It is the equilibrium between the liquid and solid phase of a material.
b. It occurs at the boiling point of a material.
c. It is the equilibrium between a material’s vapor and condensed phase.
d. It occurs at the condensation point or dew point of a material.
Answer:
C
2. How do intermolecular forces affect vapor pressure?
a. Weak intermolecular forces can be discounted in determining vapor pressure.
b. Strong intermolecular forces tend to correspond to higher vapor pressure.
c. Strong intermolecular forces tend to correspond to lower vapor pressure.
d. They do not affect it at all.
Answer:
C
3. Why do higher temperatures correspond to lower vapor pressures?
a. Because the intermolecular forces of a material are strengthened at higher
temperatures.
b. Because there is more energy in the entire system.
c. Because there is an increase in energy within the molecules of the system.
d. They do not; higher temperatures correspond to higher vapor pressures.
Answer:
D
4. What process occurs when atmospheric pressure is equal to the vapor pressure of a
liquid?
a. Condensation.
b. Boiling.
c. Evaporation.
d. Sublimation.
Answer:
B
5. Why does the melting point of water decrease with pressure?
a. Because of its extensive hydrogen bonding network.
b. Because of weak, intermolecular forces.
c. Because it has a low triple point.
d. Because it has a high vapor pressure.
Answer:
A
6. What exists simultaneously at the triple point of a material?
a. At least three solid or liquid phases of the material.
b. Any three of the phases of matter, gas, liquid, plasma, and solid.
c. The three phases of matter, solid, liquid, and gas.
d. None of the above.
Answer:
C
7. What is in equilibrium in a saturated solution?
a. Dissolved and undissolved solute.
b. Dissolved solute and solvent.
c. Dissolved, undissolved solute, and solvent.
d. Dissolved and undissolved solvent.
Answer:
A
8. How are surfactants best described?
a. As molecules having hydrophobic regions.
b. As molecules having hydrophilic regions.
c. As molecules having ambiphilic regions that can be hydrophilic or hydrophobic.
d. As molecules having hydrophobic and hydrophilic regions.
Answer:
D
9.
a.
b.
c.
Why is the solubility of a gas proportional to its partial pressure?
Because higher partial pressure increases the internal energy of the system.
Because increased partial pressure creates an increased number of in-solvent cavities.
Because increasing pressure increases the rate at which gas molecules contact a
solvent surface.
d. It is not; solubility is a state function independent of partial pressure.
Answer:
C
10. Why is the solubility of gases higher at elevated temperature?
a. Because of the increased energy throughout the system.
b. Because of increase solvent - gas interactions.
c. Because of the solvent’s increased ability to hold gas particles in solution.
d. It is not; rather solubility of gases decreases with elevated temperature.
Answer:
D
11. How is molality best expressed?
a. In moles of solute per kilograms of solvent.
b. In moles of solute per liters of solution.
c. In moles of solute per liters of solvent.
d. In moles of solute per kilograms of solution.
Answer:
A
12. Raoult’s law equates what two factors?
a. Mole fraction of a solvent in a solution and the vapor pressure of the pure solvent.
b. Mole fraction of a solute in a solution and the vapor pressure of the pure solvent.
c. Mole fraction of a solvent in a solution and the vapor pressure of the solute.
d. None of the above.
Answer:
A
13. Colligative properties of materials depend upon what factor?
a. The temperature of the system.
b. The partial pressure of gases in solution.
c. The relative amounts of solute and solvent.
d. The degree to which a system can be made to approximate an ideal gas.
Answer:
C
14. In the process of osmosis, what flows, and in what direction?
a. Solute, through a membrane, into a more concentrated solution.
b. Solute, through a membrane, into a less concentrated solution.
c. Solvent, through a membrane, into a less concentrated solution.
d. Solvent, through a membrane, into a more concentrated solution.
Answer:
C
15. Why can a minimum-boiling azeotropic mixture not be separated by fractional
distillation?
a. Because the intermolecular forces of the mixture depress the overall boiling point of
the solution.
b. Because the boiling point of the mixture is above that of each of the components.
c. Because the boiling point of the mixture is below that of each of the components.
d. It can be separated by fractional distillation.
Answer:
C