Q: 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?

$\frac{25.0\ \text{g}}{25.0\ \text{g/mol}} = 1.0\ \text{mol}$; $\frac{1.0\ \text{mol}}{0.100\ \text{kg}} = 10.0\ m$

Q: A club soda bottle contains CO2 at a concentration of 0.12 M. If the Henry’s law constant for CO2 is $3.4 \times 10^{-2}\ \text{M/atm}$, what is the pressure of CO2 required to maintain this concentration?

$\frac{0.12\ \text{M}}{3.4 \times 10^{-2}\ \text{M/atm}} = 3.5\ \text{atm}$

Q: A solution is prepared by dissolving 17.2 g of ethylene glycol ($\text{C}_2\text{H}_6\text{O}_2$) in 0.500 kg of water. The final volume of the solution is 515 mL. What is the molarity of the solution?

$\frac{0.2771\ \text{mol}}{0.515\ \text{L}} = 0.538\ M$

Q: What is the vapor pressure of a solution in which the mole fraction of the solute is 0.200 and the vapor pressure of the pure solvent is 100.0 torr? (Assume a single nonvolatile, nonelectrolyte solute.)

$P_{\text{solvent}} = 100.0\ \text{torr} \times (1 - 0.200) = 80.0\ \text{torr}$

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

$P_{\text{solvent in solution}} = P^\circ_{\text{solvent}} \cdot \chi_{\text{solvent}}$

Question 1

Which of the following statements best describes a solution?

Accepted Answer

A homogeneous mixture where atoms and molecules intermingle on the molecular and atomic scale.

Question 2

What is the primary driving force for spontaneous mixing of solutions?

Accepted Answer

The tendency of nature toward uniform mixing due to entropy.

Question 3

Which combination of solute and solvent would most likely result in a solution, according to the rule 'like dissolves like'?

Accepted Answer

A polar solute in a polar solvent.

Question 4

Which intermolecular force is primarily responsible for the solubility of ionic compounds in water?

Accepted Answer

Ion-dipole interactions

Question 5

Consider the dissolution of NaCl in water. Which step is endothermic?

Accepted Answer

Separating Na+ and Cl- ions from the solid lattice

Question 6

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

$\frac{25.0\ 	ext{g}}{25.0\ 	ext{g/mol}} = 1.0\ 	ext{mol}$; $\frac{1.0\ 	ext{mol}}{0.100\ 	ext{kg}} = 10.0\ m$

Question 7

Which of the following best explains why the solubility of most solids increases with temperature?

Accepted Answer

The dissolution process is endothermic for most solids.

Question 8

According to Henry’s Law, what happens to the solubility of a gas in water as the partial pressure of the gas above the water increases?

Accepted Answer

The solubility increases.

Question 9

A club soda bottle contains CO2 at a concentration of 0.12 M. If the Henry’s law constant for CO2 is $3.4 	imes 10^{-2}\ 	ext{M/atm}$, what is the pressure of CO2 required to maintain this concentration?

Accepted Answer

$\frac{0.12\ 	ext{M}}{3.4 	imes 10^{-2}\ 	ext{M/atm}} = 3.5\ 	ext{atm}$

Question 10

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

Accepted Answer

Molality ($m$)

Question 11

A solution is prepared by dissolving 17.2 g of ethylene glycol ($	ext{C}_2	ext{H}_6	ext{O}_2$) in 0.500 kg of water. The final volume of the solution is 515 mL. What is the molarity of the solution?

Accepted Answer

$\frac{0.2771\ 	ext{mol}}{0.515\ 	ext{L}} = 0.538\ M$

Question 12

Which property is NOT a colligative property?

Accepted Answer

Color of the solution

Question 13

What is the vapor pressure of a solution in which the mole fraction of the solute is 0.200 and the vapor pressure of the pure solvent is 100.0 torr? (Assume a single nonvolatile, nonelectrolyte solute.)

Accepted Answer

$P_{	ext{solvent}} = 100.0\ 	ext{torr} 	imes (1 - 0.200) = 80.0\ 	ext{torr}$

Question 14

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

Accepted Answer

$P_{	ext{solvent in solution}} = P^\circ_{	ext{solvent}} \cdot \chi_{	ext{solvent}}$

Question 15

A 1.7 m aqueous ethylene glycol solution is prepared. What is the freezing point of this solution? ($K_f$ for water = $1.86\ ^\circ	ext{C}/m$)

Accepted Answer

$\Delta T_f = m 	imes K_f = 1.7 	imes 1.86 = 3.16\ ^\circ	ext{C}$; 	ext{Freezing point} = 0.00 - 3.16 = -3.16\ ^\circ	ext{C}$

Question 16

What is the osmotic pressure ($\Pi$) of a 0.10 M NaCl solution at 25°C? (Assume complete dissociation, $R = 0.08206\ 	ext{L atm mol}^{-1}	ext{K}^{-1}$, $i = 2$)

Accepted Answer

$\Pi = i M R T = 2 	imes 0.10 	imes 0.08206 	imes 298 = 4.89\ 	ext{atm}$

Question 17

Which type of solution would cause a cell to shrivel due to water leaving the cell?

Accepted Answer

Hyperosmotic (Hypertonic) solution

Question 18

Which property distinguishes a colloid from a true solution?

Accepted Answer

Colloids show the Tyndall effect and do not separate on standing.

Chapter 14: Solutions – Structure, Properties, and Colligative Effects

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