Question 1

Which intermolecular force is primarily responsible for the dissolution of ionic compounds in water, as illustrated in the second image?

Accepted Answer

Ion-dipole forces

Question 2

Based on the third image, which solution would you expect to be a strong electrolyte, and why?

Accepted Answer

KCl, because it dissociates completely into ions in water

Question 3

Referencing the fourth image, what effect does adding a nonvolatile solute to water have on the vapor pressure of the solution?

Accepted Answer

It decreases the vapor pressure

Question 4

Which equation correctly expresses Raoult’s Law for a solution containing a nonvolatile solute?

Accepted Answer

$P_A = \chi_A P_A^*$

Question 5

In the context of the phase diagram shown in the last image, what happens to the freezing point of a solvent when a solute is added?

Accepted Answer

The freezing point decreases

Question 6

A solution is prepared by dissolving 10.0 g of NaCl (FW 58.44 g/mol) in 500.0 g of water. Calculate the molality of the solution.

Accepted Answer

$0.342~\mathrm{mol/kg}$

Question 7

Which of the following best explains why the vapor pressure of a solution with strong solute-solvent interactions is lower than predicted by Raoult’s Law (see image 6)?

Accepted Answer

Strong interactions keep more molecules in the liquid phase, reducing vapor pressure

Question 8

A mixture of hexane and octane is equimolar. If the vapor pressures of pure hexane and pure octane are 513 torr and 13.95 torr, respectively, what is the total vapor pressure of the mixture?

Accepted Answer

$263~\mathrm{torr}$

Question 9

Which concentration unit is defined as moles of solute per kilogram of solvent?

Accepted Answer

Molality

Question 10

A solution is made by dissolving 15.6 g of ethanol (FW 46.07 g/mol) in 625 g of water. If the boiling point elevation constant for water is $0.512~^\circ\mathrm{C}~\mathrm{kg}~\mathrm{mol}^{-1}$, what is the change in boiling point?

Accepted Answer

$0.277~^\circ\mathrm{C}$

Question 11

Which of the following statements about fractional distillation (see image 9) is correct?

Accepted Answer

It separates components based on their boiling points

Question 12

If a solution of methanol in water is 10.0% m/m methanol (FW 32.04 g/mol) and the freezing point depression constant for water is $1.86~^\circ\mathrm{C}~\mathrm{kg}~\mathrm{mol}^{-1}$, what is the freezing point of the solution?

Accepted Answer

$-6.45~^\circ\mathrm{C}$

Question 13

Which of the following best describes the effect of adding a nonvolatile solute to a solvent on its boiling point?

Accepted Answer

The boiling point increases

Question 14

Given a solution with a mole fraction of water $\chi_{H_2O} = 0.580$ and methanol $\chi_{MeOH} = 0.420$, which of the following is true?

Accepted Answer

Water is the major component

Question 15

Which of the following is a correct application of Henry’s Law for the solubility of a gas in a liquid?

Accepted Answer

$C_{gas} = k_H P_{gas}$

Question 16

A solution is prepared by dissolving MgCl$_2$ in 500.0 mL of H$_2$O. The vapor pressure above the solution is 29.6 torr, and the vapor pressure of pure water is 32.8 torr. What is the mole fraction of water in the solution?

Accepted Answer

$0.902$

Question 17

Which of the following best explains why the vapor pressure of a benzene-methanol mixture is higher than predicted by Raoult’s Law?

Accepted Answer

The benzene-methanol interactions are weaker than benzene-benzene or methanol-methanol interactions

Question 18

Which of the following is true about the direct formation of a solution as shown in the first image?

Accepted Answer

It requires maximizing strong solute-solvent interactions

Solution Properties, Raoult’s Law, and Phase Change Temperature Shifts

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