Q: A solution is prepared by dissolving 15.0 g of NaCl in 85.0 g of water. What is the mass percent of NaCl in the solution?

$$\frac{15.0}{85.0} \times 100 = 17.6\%$$

Q: A solution is made by dissolving 20.2 g of sucrose ($$C_{12}H$$_{22}$$O_{11}$) in 70.1 g of water at 35°C. The vapor pressure of pure water at 35°C is 42.2 mmHg. What is the vapor pressure of the solution? (Molar mass of sucrose = 342 g/mol)

$$P_{solution} = 0.950 \times 42.2 = 40.1$$ mmHg

Q: Calculate the boiling point elevation for a solution made by dissolving 1.00 mol of NaCl in 1.00 kg of water. ($$K_b$$ for water = $$0.512\ ^\circ C\ kg\ $$mol^{-1}$$, i$ for NaCl = 2)

$$\Delta T_b = 0.512 \times 1.00 \times 2 = 1.024\ ^\circ C$$

Q: A 0.30 M solution of sucrose at 37°C has approximately the same osmotic pressure as blood. What is the osmotic pressure of blood in mmHg? ($$R = 0.0821\ L\ atm\ $$mol^{-1}$$\ K$$^{-1}$$, T = 310$$\ K$$)

$$\Pi = 0.30 \times 0.0821 \times 310 = 7.64\ atm = 5800\ mmHg$$

Question 1

Which of the following best describes what happens at the triple point on a phase diagram?

Accepted Answer

Solid, liquid, and gas phases coexist in equilibrium.

Question 2

Which process is exothermic according to the energy diagram for phase changes?

Accepted Answer

Condensation

Question 3

A sample of water is heated from 25°C to 100°C and then boiled. Which of the following steps requires the greatest amount of energy per mole?

Accepted Answer

Vaporization

Question 4

Which of the following statements about supercritical fluids is correct?

Accepted Answer

They have properties of both liquids and gases.

Question 5

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

Accepted Answer

Ion-dipole interactions

Question 6

A solution is prepared by dissolving 15.0 g of NaCl in 85.0 g of water. What is the mass percent of NaCl in the solution?

Accepted Answer

$$\frac{15.0}{85.0} 	imes 100 = 17.6\%$$

Question 7

Which of the following best explains why road salt is effective at melting ice on winter roads?

Accepted Answer

Salt lowers the freezing point of water, causing ice to melt at lower temperatures.

Question 8

According to Henry’s Law, the solubility of a gas in a liquid is:

Accepted Answer

Directly proportional to the partial pressure of the gas above the solution.

Question 9

Which of the following will increase the solubility of oxygen in water?

Accepted Answer

Decreasing the temperature

Question 10

A solution is made by dissolving 20.2 g of sucrose ($$C_{12}H$$_{22}$$O_{11}$) in 70.1 g of water at 35°C. The vapor pressure of pure water at 35°C is 42.2 mmHg. What is the vapor pressure of the solution? (Molar mass of sucrose = 342 g/mol)

Accepted Answer

$$P_{solution} = 0.950 	imes 42.2 = 40.1$$ mmHg

Question 11

Which of the following statements about colligative properties is correct?

Accepted Answer

They depend on the number of solute particles present.

Question 12

Calculate the boiling point elevation for a solution made by dissolving 1.00 mol of NaCl in 1.00 kg of water. ($$K_b$$ for water = $$0.512\ ^\circ C\ kg\ $$mol^{-1}$$, i$ for NaCl = 2)

Accepted Answer

$$\Delta T_b = 0.512 	imes 1.00 	imes 2 = 1.024\ ^\circ C$$

Question 13

Which of the following best describes why vitamin C is water-soluble but vitamin A is fat-soluble?

Accepted Answer

Vitamin C has many polar groups that can hydrogen bond with water, while vitamin A is mostly nonpolar.

Question 14

A 0.30 M solution of sucrose at 37°C has approximately the same osmotic pressure as blood. What is the osmotic pressure of blood in mmHg? ($$R = 0.0821\ L\ atm\ $$mol^{-1}$$\ K$$^{-1}$$, T = 310$$\ K$$)

Accepted Answer

$$\Pi = 0.30 	imes 0.0821 	imes 310 = 7.64\ atm = 5800\ mmHg$$

Question 15

Which of the following is true about molality ($$m) $$and molarity ($$M$$)?

Accepted Answer

Molality does not change with temperature, while molarity does.

Question 16

A solution is prepared by mixing 18.0 g of water ($$H_2O) $$with 46.0 g of ethanol ($$C_2H_5OH). $$What is the mole fraction of ethanol?

Accepted Answer

$$\chi_{ethanol} = \frac{1.00}{1.00+1.00} = 0.50$$

Question 17

Which of the following best describes a supersaturated solution?

Accepted Answer

A solution that contains more dissolved solute than its equilibrium solubility and is unstable.

Question 18

Which of the following is the correct expression for the vapor pressure lowering ($$\Delta P) $$according to Raoult’s Law?

Accepted Answer

$$\Delta P = P^0$_{solvent} \chi_{solute}$$

Phase Chemistry and Colligative Properties: Study Notes for General Chemistry

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