Question 1

Which of the following best describes the phenomenon of freezing point depression?

Accepted Answer

The freezing point of a solvent decreases when a solute is added.

Question 2

Which equation correctly represents the freezing point depression for a solution?

Accepted Answer

$$\Delta T_f = K_f \cdot m \cdot i$$

Question 3

A solution is prepared by dissolving 110.7 g of glucose ($$C_6H_{12}O_6$) in 302.6 g of water. Given K_f$ for water is 1.86$$\ \mathrm{^\circ C\,kg\,$$mol^{-1}$$}$$, what is the freezing point depression ($$\Delta T_f$$) of the solution? (Molar mass of glucose = 180$$\ \mathrm{g\,$$mol^{-1}$$}$$)

Accepted Answer

$$-1.78\ ^\circ \mathrm{C}$$

Question 4

If the normal freezing point of water is $$0^\circ \mathrm{C}$$, what will be the freezing point of a solution with $$\Delta T_f = -3.0^\circ \mathrm{C}$$?

Accepted Answer

$$-3.0^\circ \mathrm{C}$$

Question 5

A solution is made by dissolving 28.3 g of ethylene glycol ($$C_2H_6O_2) in 97.2 mL of $$water (density = $$1.00\ \mathrm{g\,mL$$^{-1}$$}). $$What is the molality ($$m) of $$the solution? (Molar mass of ethylene glycol = $$62.07\ \mathrm{g\,$$mol^{-1}$$})$$

Accepted Answer

$$2.91\ \mathrm{mol\,kg$$^{-1}$$}$$

Question 6

Which of the following statements about the van't Hoff factor ($$i) is $$correct for glucose dissolved in water?

Accepted Answer

$$i = 1$$ because glucose does not dissociate in water.

Question 7

A solution is prepared by dissolving 825 g of an unknown non-electrolyte in 3.45 L of water, resulting in a freezing point depression of $$2.89^\circ \mathrm{C}. If$$ $$K_f$$ for water is $$1.86\ ^\circ \mathrm{C\,kg\,$$mol^{-1}$$}$$, what is the molar mass of the unknown? (Assume density of water = $$1.00\ \mathrm{g\,mL$$^{-1}$$})$$

Accepted Answer

$$600\ \mathrm{g\,$$mol^{-1}$$}$$

Question 8

Which of the following would result in the greatest freezing point depression for 1 kg of water?

Accepted Answer

Adding 1 mol of sodium chloride ($$NaCl)$$

Question 9

If 1.00 mol of $$NaCl is $$dissolved in 1.00 kg of water, what is the expected freezing point depression? ($$K_f$$ for water = $$1.86\ ^\circ \mathrm{C\,kg\,$$mol^{-1}$$}$$; $$NaCl$$ dissociates completely)

Accepted Answer

$$3.72^\circ \mathrm{C}$$

Question 10

A patient is treated for antifreeze poisoning (ethylene glycol, $$C_2H_6O_2). If 100 g of $$ethylene glycol is dissolved in 1.00 kg of water, what is the freezing point of the solution? ($$K_f$$ for water = $$1.86\ ^\circ \mathrm{C\,kg\,$$mol^{-1}$$}$$, molar mass of ethylene glycol = $$62.07\ \mathrm{g\,$$mol^{-1}$$})$$

Accepted Answer

$$-2.99^\circ \mathrm{C}$$

Question 11

Which of the following best explains why adding salt to icy roads helps melt the ice?

Accepted Answer

Salt decreases the freezing point of water, so ice melts at a lower temperature.

Question 12

A solution is prepared by dissolving 50.0 g of a non-electrolyte in 500.0 g of water. The freezing point of the solution is $$-1.86^\circ \mathrm{C}. If$$ $$K_f$$ for water is $$1.86\ ^\circ \mathrm{C\,kg\,$$mol^{-1}$$}$$, what is the molar mass of the solute?

Accepted Answer

$$100.0\ \mathrm{g\,$$mol^{-1}$$}$$

Question 13

Which variable does NOT affect the magnitude of freezing point depression in a solution?

Accepted Answer

The temperature at which the solution is prepared

Question 14

A solution is made by dissolving 0.5 mol of $$Na_2SO_4 in 1.0 kg of $$water. What is the expected freezing point depression? ($$K_f$$ for water = $$1.86\ ^\circ \mathrm{C\,kg\,$$mol^{-1}$$}$$; $$Na_2SO_4$$ dissociates into 3 ions)

Accepted Answer

$$2.79^\circ \mathrm{C}$$

Question 15

Which of the following is the correct definition of molality ($$m$$)?

Accepted Answer

Moles of solute per kilogram of solvent

Question 16

A laboratory technician needs to prepare a solution with a freezing point of $$-10^\circ \mathrm{C}$$ using ethylene glycol ($$C_2H_6O_2) $$and 1.00 kg of water. How many moles of ethylene glycol are required? ($$K_f$$ for water = $$1.86\ ^\circ \mathrm{C\,kg\,$$mol^{-1}$$})$$

Accepted Answer

$$5.38\ \mathrm{mol}$$

Freezing Point Depression in Solutions

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