Q: A solution is made by dissolving 5.00 g of glucose ($$C_6H_{12}O_6$) in 100.0 g of water at 90°C. The vapor pressure of pure water at 90°C is 524 torr. What is the vapor pressure of the solution? (Molar mass of glucose = 180.16 g/mol)

$$P_{\text{solution}} = 501 \text{ torr}$$

Q: Which equation correctly relates the vapor pressure of a solution to the mole fraction of the solvent and the vapor pressure of the pure solvent?

$$P_{\text{solution}} = x_{\text{solvent}} P^*_{\text{solvent}}$$

Question 1

Which of the following best describes the condition for dynamic equilibrium in a closed flask containing a volatile liquid?

Accepted Answer

The rate of evaporation equals the rate of condensation.

Question 2

Which of the following substances has the lowest vapor pressure at 25°C, based on the provided data?

Accepted Answer

Mercury

Question 3

A liquid boils when its vapor pressure equals atmospheric pressure. At sea level (1 atm), which liquid will boil at the lowest temperature?

Accepted Answer

Diethyl ether

Question 4

Which intermolecular force is primarily responsible for the high boiling point of water compared to other similar-sized molecules?

Accepted Answer

Hydrogen bonding

Question 5

According to the Clausius-Clapeyron equation, which of the following statements is correct?

Accepted Answer

A plot of $$\ln P$$ versus $$1/T$$ yields a straight line with a slope of $$-\Delta H_{	ext{vap}}/R.$$

Question 6

Which of the following best explains why the vapor pressure of a solution containing a nonvolatile solute is lower than that of the pure solvent?

Accepted Answer

The solute reduces the number of solvent molecules at the surface, lowering the tendency to vaporize.

Question 7

A solution is made by dissolving 5.00 g of glucose ($$C_6H_{12}O_6$) in 100.0 g of water at 90°C. The vapor pressure of pure water at 90°C is 524 torr. What is the vapor pressure of the solution? (Molar mass of glucose = 180.16 g/mol)

Accepted Answer

$$P_{	ext{solution}} = 501 	ext{ torr}$$

Question 8

Which of the following mixtures will show a positive deviation from Raoult’s Law?

Accepted Answer

A mixture where the components have weaker interactions with each other than with themselves.

Question 9

Which of the following best describes the effect of increasing temperature on the vapor pressure of a liquid?

Accepted Answer

Vapor pressure increases as temperature increases.

Question 10

Which of the following statements about the boiling points of the following substances is correct? (CH$$_3NH$_2$$, CH$$_3$$OCH$$_3$$, CH$$_4$$, SiH$$_4$$, Ne)

Accepted Answer

Ne \u003c CH$$_4$$ \u003c SiH$$_4$$ \u003c CH$$_3$$OCH$$_3$$ \u003c CH$$_3NH$_2$$

Question 11

Which of the following best explains why diethyl ether has a lower boiling point than water?

Accepted Answer

Diethyl ether has weaker intermolecular forces than water.

Question 12

Which equation correctly relates the vapor pressure of a solution to the mole fraction of the solvent and the vapor pressure of the pure solvent?

Accepted Answer

$$P_{	ext{solution}} = x_{	ext{solvent}} P^*_{	ext{solvent}}$$

Question 13

Which of the following best describes the relationship between intermolecular forces and vapor pressure?

Accepted Answer

As intermolecular forces increase, vapor pressure decreases.

Question 14

A closed flask contains a liquid and its vapor at equilibrium. What will happen if the temperature is increased?

Accepted Answer

The rate of evaporation will increase until a new equilibrium is established at a higher vapor pressure.

Question 15

Which of the following best explains why the vapor pressure of mercury is much lower than that of water at 25°C?

Accepted Answer

Mercury has stronger intermolecular forces than water.

Question 16

Which of the following is a correct application of Raoult’s Law for an ideal solution of two volatile liquids, A and B?

Accepted Answer

$$P = x_A P^*_A + x_B P^*_B$$

Question 17

Which of the following best describes the effect of adding a nonvolatile solute to a solvent?

Accepted Answer

The freezing point of the solution decreases.

Question 18

Which of the following best explains why the vapor pressure of a solution deviates from Raoult’s Law in the case of strong solute-solvent attractions?

Accepted Answer

The vapor pressure is lower than predicted due to stronger interactions.

Phase Equilibria, Vapor Pressure, and Chemical Equilibrium: Study Guide

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