Question 1

Which of the following statements best describes the triple point on a phase diagram?

Accepted Answer

It is the unique temperature and pressure at which all three phases (solid, liquid, and gas) coexist in equilibrium.

Question 2

Why does the melting point of ice decrease as pressure increases, as shown in the phase diagram of water?

Accepted Answer

Because the solid-liquid equilibrium line for water has a negative slope, which is unusual for solids.

Question 3

A solution is made by dissolving 36.0 g of glucose ($$\mathrm{C_6H_{12}O_6$}) in 14.4 g of $$water. If the vapor pressure of pure water at $$20^\circ\mathrm{C} is 17.5 $$torr, what is the partial vapor pressure of water above the solution? (Molar mass of glucose = 180 g/mol, molar mass of water = 18 g/mol)

Accepted Answer

$$14.0$$ torr

Question 4

Which of the following best explains why the boiling point of a solution is higher than that of the pure solvent?

Accepted Answer

The addition of a nonvolatile solute lowers the vapor pressure, requiring a higher temperature for the vapor pressure to reach atmospheric pressure.

Question 5

Which equation correctly expresses Raoult’s Law for the vapor pressure of a solvent in an ideal solution?

Accepted Answer

$$P_A = X_A P_A^0$

Question 6

A red blood cell is placed in a hypertonic solution. What will happen to the cell and why?

Accepted Answer

Water will flow out of the cell, causing it to shrink (crenation).

Question 7

Which of the following is NOT a colligative property?

Accepted Answer

Viscosity increase

Question 8

Calculate the freezing point depression ($$\Delta T_f) $$for a solution containing 5.15 g of benzene ($$\mathrm{C_6H_6}$$, molar mass = 78 g/mol) dissolved in 50.0 g of carbon tetrachloride ($$\mathrm{$$CCl_4$$}$$). $$K_f$$ for $$\mathrm{$$CCl_4$$} is$$ $$29.8\ ^\circ\mathrm{C}/m.$$

Accepted Answer

$$1.97\ ^\circ\mathrm{C}$$

Question 9

Which of the following best describes an ideal solution?

Accepted Answer

A solution that obeys Raoult’s Law at all concentrations.

Question 10

A solution is prepared by mixing 52.1 g of $$\mathrm{C_6H_5Cl} ($$molar mass = 112.5 g/mol) and 38.4 g of $$\mathrm{C_6H_5Br} ($$molar mass = 157 g/mol). The vapor pressure of pure $$\mathrm{C_6H_5Cl} is 347 $$torr and that of pure $$\mathrm{C_6H_5Br} is 133 $$torr at $$25^\circ\mathrm{C}. $$What is the partial vapor pressure of $$\mathrm{C_6H_5Cl} in $$the solution? (Assume ideal solution.)

Accepted Answer

$$214$$\ torr

Question 11

Which of the following statements about the phase diagram of $$\mathrm{CO_2$} is $$correct?

Accepted Answer

Solid $$\mathrm{CO_2$}$$ sublimes at $$-78^\circ\mathrm{C} at 1 $$atm.

Question 12

Which of the following will give the lowest freezing point when added to 1 kg of water?

Accepted Answer

2 mol of $$\mathrm{KCl}$$

Question 13

A solution is made by dissolving 75.0 g of sucrose ($$\mathrm{C$$_{12}$$H_{22}O$$_{11}}$$) in 180.0 g of water. The vapor pressure of pure water at 27$$^\circ\mathrm{C}$ is 26.7 torr. What is the mole fraction of sucrose in the solution? (Molar mass of sucrose = 342 g/mol, molar mass of water = 18 g/mol)

Accepted Answer

0.023

Question 14

Which of the following best describes osmosis in biological systems?

Accepted Answer

Solvent moves from low solute concentration to high solute concentration through a semipermeable membrane.

Question 15

Which of the following is the correct formula for boiling point elevation?

Accepted Answer

$$\Delta T_b = i K_b m$$

Question 16

If you have a solution with a higher concentration of solute outside a cell than inside, what will happen to the cell?

Accepted Answer

It will lose water and shrink.

Question 17

Which of the following best explains why molality is used instead of molarity in colligative property calculations?

Accepted Answer

Molality does not change with temperature because it is based on mass, not volume.

Question 18

Which of the following is true about the critical point on a phase diagram?

Accepted Answer

It is the highest temperature and pressure at which a liquid can exist.

Phase Equilibrium and Colligative Properties: Study Notes for Introductory Chemistry

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