Q: Which equation correctly expresses Raoult’s Law for the vapor pressure of a solvent in a solution?

$$P_{\text{solution}} = X_{\text{solvent}} P^\circ_{\text{solvent}}$$

Question 1

Wood frogs can survive freezing temperatures because their blood contains a high concentration of glucose. What colligative property is primarily responsible for preventing their blood from freezing?

Accepted Answer

Freezing point depression

Question 2

Which of the following best explains why oil does not dissolve in water?

Accepted Answer

Oil is nonpolar and water is polar, so their intermolecular forces are incompatible.

Question 3

A solution is prepared by dissolving 25.0 g of a solute (molar mass = 25.0 g/mol) in 100.0 g of solvent. What is the molality of the solution?

Accepted Answer

$$1.0\ \mathrm{m}$$

Question 4

Which of the following statements about entropy and mixing of ideal gases is correct?

Accepted Answer

Ideal gases mix because mixing increases their entropy.

Question 5

Which vitamin structure is most likely to be fat-soluble?

Accepted Answer

A molecule with mostly nonpolar $$\mathrm{C-H}$$ and $$\mathrm{C-C}$$ bonds and few polar groups.

Question 6

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

Accepted Answer

The vapor pressure of the solution decreases.

Question 7

A solution contains 99.5 g of sucrose ($$\mathrm{C$$_{12}$$H_{22}O$$_{11}}$$) and 300.0 mL of water. The vapor pressure of pure water at 25$$^\circ\mathrm{C}$ is 23.8 torr. What is the first step in calculating the vapor pressure of the solution?

Accepted Answer

Calculate the number of moles of sucrose and water.

Question 8

Which of the following solutions will have the highest boiling point?

Accepted Answer

$$0.50\ \mathrm{M}$$ NaCl

Question 9

Which equation correctly expresses Raoult’s Law for the vapor pressure of a solvent in a solution?

Accepted Answer

$$P_{	ext{solution}} = X_{	ext{solvent}} P^\circ_{	ext{solvent}}$$

Question 10

A solution is prepared by dissolving 17.2 g of ethylene glycol ($$\mathrm{C_2H_6O_2}$$, molar mass = 62.07 g/mol) in 0.500 kg of water. The final volume is 515 mL. What is the molality of the solution?

Accepted Answer

$$0.555\ \mathrm{m}$$

Question 11

Which of the following best describes a supersaturated solution?

Accepted Answer

A solution that contains more solute than can normally dissolve at that temperature.

Question 12

Which of the following statements about the effect of temperature on solubility is correct?

Accepted Answer

The solubility of gases in water decreases as temperature increases.

Question 13

Which of the following is the correct formula for calculating osmotic pressure ($$\pi) of a $$solution?

Accepted Answer

$$\pi = MRT$$

Question 14

A solution is made by dissolving 1.50 g of ethylene glycol in 50.0 mL of water at $$25^\circ\mathrm{C}. $$What is the main colligative property that would allow you to determine the molar mass of ethylene glycol from this solution?

Accepted Answer

Osmotic pressure

Question 15

Which of the following best describes why the experimentally measured van’t Hoff factor ($$i) $$for an ionic compound is often less than the theoretical value?

Accepted Answer

Some ions pair together in solution, reducing the number of particles.

Question 16

A solution contains equal moles of two volatile liquids, A and B. The vapor pressure of pure A is 100 mmHg, and pure B is 200 mmHg. The measured vapor pressure of the solution is 120 mmHg. What does this indicate about the interactions in the solution?

Accepted Answer

Solute-solvent interactions are weaker than solute-solute and solvent-solvent interactions.

Question 17

Which of the following best describes a hyperosmotic (hypertonic) solution relative to a cell?

Accepted Answer

It has a higher osmotic pressure than the cell, causing the cell to shrivel.

Question 18

Which of the following is the correct equation for freezing point depression?

Accepted Answer

$$\Delta T_f = i K_f m$$

Question 19

A 10.5% by mass glucose solution has a density of $$1.03\ \mathrm{g/mL}. $$What is the first step in calculating its molarity?

Accepted Answer

Assume 100 g solution, then use density to find the volume in liters.

Chapter 13: Solutions – Structure, Properties, and Colligative Effects

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