Q: A solution is prepared by mixing 50 g of KNO$$_3$$ with 150 g of water at 25$$^ ext{o}C. $$The vapor pressure of pure water is 23.8 torr at this temperature. If the mole fraction of water is 0.944, what is the vapor pressure of the solution according to Raoult’s Law?

$$P_{\text{solution}} = 0.944 \times 23.8 = 22.5$$ torr

Q: Which equation correctly describes the boiling point elevation for a solution?

$$\Delta T_b = i K_b m_{\text{solute}}$$

Q: Which of the following is the correct expression for the mole fraction of solute in a solution?

$$c_{\text{solute}} = \frac{n_{\text{solute}}}{n_{\text{solute}} + n_{\text{solvent}}}$$

Question 1

Which of the following concentration units will change when the temperature of a solution is increased?

Accepted Answer

Molarity

Question 2

When a nonvolatile solute such as KNO$$_3 is $$added to water, what happens to the vapor pressure of the solution?

Accepted Answer

Vapor pressure will decrease

Question 3

A solution is prepared by mixing 50 g of KNO$$_3$$ with 150 g of water at 25$$^	ext{o}C. $$The vapor pressure of pure water is 23.8 torr at this temperature. If the mole fraction of water is 0.944, what is the vapor pressure of the solution according to Raoult’s Law?

Accepted Answer

$$P_{	ext{solution}} = 0.944 	imes 23.8 = 22.5$$ torr

Question 4

Which of the following aqueous solutions will have the lowest freezing point?

Accepted Answer

0.3 m Na$$_3PO$_4$$

Question 5

A nonvolatile, nonelectrolyte solute (0.2 g) is dissolved in 4 g of benzene, causing the freezing point to decrease from 5.5$$^	ext{o}C to 5.1$^	ext{o}C. If$$ $$K_f$$ for benzene is 5.12 $$^	ext{o}C kg $$mol$$^{-1}$$, what is the molar mass of the solute?

Accepted Answer

640 g/mol

Question 6

Which equation correctly describes the boiling point elevation for a solution?

Accepted Answer

$$\Delta T_b = i K_b m_{	ext{solute}}$$

Question 7

Which of the following best explains why NaCl dissolves in water even though $$\Delta H_{	ext{solution}} is $$slightly positive?

Accepted Answer

The entropy increase ($$\Delta S) $$upon dissolution makes $$\Delta G$$ negative

Question 8

Which of the following statements about the solubility of gases in water is correct?

Accepted Answer

Solubility decreases with increasing temperature

Question 9

A solution is prepared by mixing two volatile liquids, A and B. If the solution feels colder when the substances are mixed, what deviation from Raoult’s Law would you expect?

Accepted Answer

Positive deviation

Question 10

Which of the following best describes the principle 'like dissolves like'?

Accepted Answer

Polar solutes dissolve in polar solvents, nonpolar solutes dissolve in nonpolar solvents

Question 11

Which equation is used to calculate the osmotic pressure ($$\Pi) of a $$solution?

Accepted Answer

$$\Pi = iMRT$$

Question 12

A solution is made by dissolving 0.1 mol of glucose (C$$_6H$_{12}O$_6) in 1.0 kg of $$water. What is the expected van’t Hoff factor ($$i) $$for this solution?

Accepted Answer

1

Question 13

Which of the following will NOT affect the molality of a solution?

Accepted Answer

Change in temperature

Question 14

Which of the following best describes what happens during osmosis?

Accepted Answer

Solvent moves from the pure solvent side to the solution side through a semipermeable membrane

Question 15

Which of the following is true for a supersaturated solution?

Accepted Answer

It contains more solute than is present in a saturated solution

Question 16

Which of the following is a colligative property?

Accepted Answer

Boiling point elevation

Question 17

A solution is prepared by mixing 0.51 mol of benzene (C$$_6H$_6) $$and 0.80 mol of toluene (C$$_7H$_8) at 25$^	ext{o}C. If $$the vapor pressures of pure benzene and toluene are 95 torr and 27 torr, respectively, what is the total vapor pressure of the solution?

Accepted Answer

53 torr

Question 18

Which of the following best explains a negative deviation from Raoult’s Law?

Accepted Answer

Strong interactions between solute and solvent

Question 19

Which of the following will increase the solubility of a gas in water?

Accepted Answer

Increasing the external pressure

Question 20

Which of the following is the correct expression for the mole fraction of solute in a solution?

Accepted Answer

$$c_{	ext{solute}} = \frac{n_{	ext{solute}}}{n_{	ext{solute}} + n_{	ext{solvent}}}$$

Chapter 14 & 17: Solutions and Colligative Properties

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