Q: A solution is prepared by dissolving 25.0 g of KMnO$$_4 ($$molar mass = 158.034 g/mol) in enough water to make 250.0 g of solution. What is the molality of the solution?

$$m = \frac{0.158~\text{mol}}{0.225~\text{kg}} = 0.702~\text{mol/kg}$$

Q: A 25.0% by mass HNO$$_3$$ solution (density = 1.344 g/mL) is prepared. What is the molarity of HNO$$_3 in $$the solution? (Molar mass HNO$$_3 = 63.013 g/$$mol)

$$M = \frac{25.0~\text{g}}{63.013~\text{g/mol}} \div 0.0744~\text{L} = 5.36~\text{mol/L}$$

Q: A solution is made by dissolving 250.0 g of benzene (C$$_6H$_6$$, molar mass = 78.10 g/mol) and 50.1 g of lauric acid (C$$_{12}H$_{24}O$_2$$, molar mass = 200.3 g/mol). The vapor pressure of pure benzene at 20.0 $$^\circC is 74.6 $$mmHg. What is the vapor pressure of benzene above the solution?

$$P = 74.6~\text{mmHg} \times X_{C_6H_6} = 74.6~\text{mmHg} \times 0.886 = 66.1~\text{mmHg}$$

Q: A saline solution is prepared by dissolving 9.00 g of NaCl (molar mass = 58.44 g/mol) in enough water to make 1.00 L of solution. What is the osmotic pressure of this solution at 37.0 $$^\circC$$? ($$R = 0.08206~\text{L} \cdot \text{atm}/\text{mol} \cdot \text{K})$$

$$\pi = iMRT = 2 \times 0.154~\text{mol/L} \times 0.08206~\text{L} \cdot \text{atm}/\text{mol} \cdot \text{K} \times 310~\text{K} = 7.82~\text{atm}$$

Question 1

Which of the following best describes a saturated solution?

Accepted Answer

A solution in which no more solute can dissolve at a given temperature and pressure.

Question 2

Which intermolecular force is primarily responsible for the dissolution of NaCl in water?

Accepted Answer

Ion-dipole interactions

Question 3

A solution is prepared by dissolving 25.0 g of KMnO$$_4 ($$molar mass = 158.034 g/mol) in enough water to make 250.0 g of solution. What is the molality of the solution?

Accepted Answer

$$m = \frac{0.158~	ext{mol}}{0.225~	ext{kg}} = 0.702~	ext{mol/kg}$$

Question 4

Which of the following statements about colligative properties is correct?

Accepted Answer

They depend only on the number of solute particles in solution, not their identity.

Question 5

A 25.0% by mass HNO$$_3$$ solution (density = 1.344 g/mL) is prepared. What is the molarity of HNO$$_3 in $$the solution? (Molar mass HNO$$_3 = 63.013 g/$$mol)

Accepted Answer

$$M = \frac{25.0~	ext{g}}{63.013~	ext{g/mol}} \div 0.0744~	ext{L} = 5.36~	ext{mol/L}$$

Question 6

What happens to the boiling point and freezing point of water when NaCl is dissolved in it?

Accepted Answer

The boiling point increases and the freezing point decreases.

Question 7

A solution contains 471 g of acetic acid (HC$$_2H$_3O$_2) $$and 117 g of water. Which compound is the solvent, and what is the freezing point of the solution? (K$$_f$$ for H$$_2O = 1.86$$ $$^\circC/$$molal, K$$_f$$ for HC$$_2H$_3O$_2 = 3.59$$ $$^\circC/$$molal)

Accepted Answer

Water is the solvent; use K$$_f$$ for H$$_2O to $$calculate the freezing point.

Question 8

Which of the following best explains why the vapor pressure of a pure liquid increases with temperature?

Accepted Answer

As temperature increases, more molecules have enough kinetic energy to escape into the vapor phase.

Question 9

Which of the following aqueous solutions will have the lowest freezing point? (Assume complete dissociation for ionic compounds.)

Accepted Answer

0.15 mol/kg CaCl$$_2$$

Question 10

A solution is made by dissolving 250.0 g of benzene (C$$_6H$_6$$, molar mass = 78.10 g/mol) and 50.1 g of lauric acid (C$$_{12}H$_{24}O$_2$$, molar mass = 200.3 g/mol). The vapor pressure of pure benzene at 20.0 $$^\circC is 74.6 $$mmHg. What is the vapor pressure of benzene above the solution?

Accepted Answer

$$P = 74.6~	ext{mmHg} 	imes X_{C_6H_6} = 74.6~	ext{mmHg} 	imes 0.886 = 66.1~	ext{mmHg}$$

Question 11

A saline solution is prepared by dissolving 9.00 g of NaCl (molar mass = 58.44 g/mol) in enough water to make 1.00 L of solution. What is the osmotic pressure of this solution at 37.0 $$^\circC$$? ($$R = 0.08206~	ext{L} \cdot 	ext{atm}/	ext{mol} \cdot 	ext{K})$$

Accepted Answer

$$\pi = iMRT = 2 	imes 0.154~	ext{mol/L} 	imes 0.08206~	ext{L} \cdot 	ext{atm}/	ext{mol} \cdot 	ext{K} 	imes 310~	ext{K} = 7.82~	ext{atm}$$

Question 12

Which of the following best describes the effect of increasing pressure on the solubility of a gas in a liquid?

Accepted Answer

The solubility of the gas increases.

Question 13

Which of the following is the correct formula for calculating the mole fraction of a component A in a solution?

Accepted Answer

$$X_A = \frac{	ext{mol A}}{	ext{total moles}}$$

Question 14

A patient receives an intravenous (IV) solution that is hypotonic relative to their blood plasma. What is the most likely effect on the patient's red blood cells?

Accepted Answer

Water will enter the cells, causing them to swell and possibly burst.

Question 15

Which of the following best explains why adding a nonvolatile solute to a solvent lowers the solvent's vapor pressure?

Accepted Answer

The solute particles occupy surface sites, reducing the number of solvent molecules able to escape into the vapor phase.

Question 16

Which of the following equations correctly expresses Raoult’s Law for the vapor pressure of a solution?

Accepted Answer

$$P_A = P_A^\circ X_A$$

Question 17

A solution is prepared by dissolving 7.20 g of C$$_2H$_6O$_2 ($$molar mass = 62.07 g/mol) in 3546 g of water. What is the mole fraction of C$$_2H$_6O$_2 in $$the solution?

Accepted Answer

$$X_{C_2H_6O_2} = \frac{0.116~	ext{mol}}{0.116~	ext{mol} + 197~	ext{mol}} = 0.00059$$

Question 18

Which of the following best describes the entropy change when a solid solute dissolves in a liquid solvent?

Accepted Answer

Entropy increases because the solute particles become more dispersed.

Question 19

A chemist needs to prepare 500.0 mL of a 0.200 M NaCl solution. How many grams of NaCl are required? (Molar mass = 58.44 g/mol)

Accepted Answer

$$0.200~	ext{mol/L} 	imes 0.500~	ext{L} 	imes 58.44~	ext{g/mol} = 5.84~	ext{g}$$

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