Question 1

Raoult's Law relates the vapor pressure of a solvent above a solution to the mole fraction of the solvent and the vapor pressure of the pure solvent.

Accepted Answer

A) True 
 B)False

Question 2

Select the weakest electrolyte from the following set.

Accepted Answer

A)  Na2 SO4 
B)  KCl 
C)  CH3 CH2 COOH, propionic acid 
D)  CaCl2 
E)  LiOH

Question 3

Calculate the vapor pressure of a solution prepared by dissolving 0.500 mol of a non-volatile solute in 275 g of hexane (  = 86.18 g/mol) at 49.6°C. P°hexane = 400.0 torr at 49.6°C.

Accepted Answer

A)  54 torr 
B)  154 torr 
C)  246 torr 
D)  346 torr 
E)  400. torr

Question 4

Colligative properties depend on

Accepted Answer

A)  the chemical properties of the solute. 
B)  the chemical properties of the solvent. 
C)  the masses of the individual ions. 
D)  the molar mass of the solute. 
E)  the number of particles dissolved.

Question 5

Benzaldehyde (  = 106.1 g/mol), also known as oil of almonds, is used in the manufacture of dyes and perfumes and in flavorings. What would be the freezing point of a solution prepared by dissolving 75.00 g of benzaldehyde in 850.0 g of ethanol? Kf = 1.99°C/m, freezing point of pure ethanol = -117.3°C.

Accepted Answer

A)  -117.5°C 
B)  -118.7°C 
C)  -119.0°C 
D)  -120.6°C 
E)  < -121°C

Question 6

Potassium fluoride is used for frosting glass. Calculate the molarity of a solution prepared by dissolving 78.6 g of KF in enough water to produce 225 mL of solution.

Accepted Answer

A)  0.304 M 
B)  0.349 M 
C)  1.35 M 
D)  3.29 M 
E)  6.01 M

Question 7

The solubility of gases in water increases with increase in the pressure of the gas.

Accepted Answer

A) True 
 B)False

Question 8

Heats of solution may be either positive or negative.

Accepted Answer

A) True 
 B)False

Question 9

A solution of sucrose (sugar) in water is in equilibrium with solid sucrose. If more solid sucrose is now added, with stirring,

Accepted Answer

A)  the concentration of the solution will increase. 
B)  the concentration of the solution will decrease. 
C)  the concentration of the solution will remain the same. 
D)  the volume of solution will increase. 
E)  a supersaturated solution will be produced.

Question 10

From the following list of aqueous solutions and water, select the one with the highest boiling point.

Accepted Answer

A)  1.0 m KNO3 
B)  0.75 m NaCl 
C)  0.75 m CuCl2 
D)  2.0 m C12H22O11 (sucrose) 
E)  pure water

Question 11

If a solute dissolves in an endothermic process

Accepted Answer

A)  H bonds must exist between solvent and solute. 
B)  strong ion-dipole forces must exist in the solution. 
C)  the solute must be a gas. 
D)  the entropy of the solution is immaterial. 
E)  the entropy of the solution must be greater than that of its pure components.

Question 12

Which of the following pairs of ions is arranged so that the ion with the larger (i.e., more negative) heat of hydration is listed first?

Accepted Answer

A)  Br-, K+ 
B)  Mg2+, Sr 2+ 
C)  Ca2+, Sc3+ 
D)  Na+, Li+ 
E)  None of these choices are correct.

Question 13

Children under the age of 6 with more than 0.10 ppm of lead in their blood can suffer a reduction in I.Q. or have behavior problems. What is the molality of a solution which contains 0.10 ppm of lead?

Accepted Answer

A)  4.8 × 10-10 m 
B)  4.8 × 10-7 m 
C)  4.8 × 10-4 m 
D)  4.8 × 10-1 m 
E)  None of these choices are correct.

Question 14

Isoamyl salicylate (  = 208.25 g/mol) has a pleasant aroma and is used in perfumes and soaps. Which of the following combinations gives a 0.75 m solution of isoamyl salicylate in ethyl alcohol (d = 0.7893 g/mL)?

Accepted Answer

A)  117.2 g isoamyl salicylate in 950.0 mL of ethyl alcohol 
B)  117.2 g isoamyl salicylate in 750.0 mL of ethyl alcohol 
C)  117.2 g isoamyl salicylate in 750.0 mL of solution 
D)  117.2 g isoamyl salicylate in 592.0 g of ethyl alcohol 
E)  None of these choices are correct.

Question 15

Based only on the relative lattice energies of the compounds below, which one would be expected to have the lowest solubility in water?

Accepted Answer

A)  NaBr 
B)  CaS 
C)  NaOH 
D)  KI 
E)  CsCl

Question 16

Human blood has a molar concentration of solutes of 0.30 M. What is the osmotic pressure of blood at 25°C?

Accepted Answer

A)  0.012 atm 
B)  0.62 atm 
C)  6.8 atm 
D)  7.3 atm 
E)  >10. atm

Question 17

Heats of hydration may be either positive or negative.

Accepted Answer

A) True 
 B)False

Question 18

Diethyl ether has a vapor pressure of 400.0 torr at 18°C. When a sample of benzoic acid is dissolved in ether, the vapor pressure of the solution is 342 torr. What is the mole fraction of benzoic acid in the solution?

Accepted Answer

A)  0.0169 
B)  0.0197 
C)  0.145 
D)  0.855 
E)  None of these choices are correct.

Question 19

Gases with high boiling points tend to be more soluble in water than ones with low boiling points.

Accepted Answer

A) True 
 B)False

Question 20

A solution of ethanol (C2H6O) in water is sometimes used as a disinfectant. 1.00 L of this solution contains 553 g of ethanol and 335 g of water. What is the molality of the ethanol in this solution?

Accepted Answer

A)  0.392 m 
B)  0.608 m 
C)  13.5 m 
D)  33.6 m 
E)  35.8 m

Exam 13: The Properties of Mixtures Solutions and Colloids

Raoult's Law relates the vapor pressure of a solvent above a solution to the mole fraction of the solvent and the vapor pressure of the pure solvent.

Select the weakest electrolyte from the following set.

Calculate the vapor pressure of a solution prepared by dissolving 0.500 mol of a non-volatile solute in 275 g of hexane ( = 86.18 g/mol) at 49.6°C. P°_hexane = 400.0 torr at 49.6°C.

Colligative properties depend on

Potassium fluoride is used for frosting glass. Calculate the molarity of a solution prepared by dissolving 78.6 g of KF in enough water to produce 225 mL of solution.

The solubility of gases in water increases with increase in the pressure of the gas.

Heats of solution may be either positive or negative.

A solution of sucrose (sugar) in water is in equilibrium with solid sucrose. If more solid sucrose is now added, with stirring,

From the following list of aqueous solutions and water, select the one with the highest boiling point.

If a solute dissolves in an endothermic process

Which of the following pairs of ions is arranged so that the ion with the larger (i.e., more negative) heat of hydration is listed first?

Children under the age of 6 with more than 0.10 ppm of lead in their blood can suffer a reduction in I.Q. or have behavior problems. What is the molality of a solution which contains 0.10 ppm of lead?

Isoamyl salicylate ( = 208.25 g/mol) has a pleasant aroma and is used in perfumes and soaps. Which of the following combinations gives a 0.75 m solution of isoamyl salicylate in ethyl alcohol (d = 0.7893 g/mL) ?

Based only on the relative lattice energies of the compounds below, which one would be expected to have the lowest solubility in water?

Human blood has a molar concentration of solutes of 0.30 M. What is the osmotic pressure of blood at 25°C?

Heats of hydration may be either positive or negative.

Diethyl ether has a vapor pressure of 400.0 torr at 18°C. When a sample of benzoic acid is dissolved in ether, the vapor pressure of the solution is 342 torr. What is the mole fraction of benzoic acid in the solution?

Gases with high boiling points tend to be more soluble in water than ones with low boiling points.

A solution of ethanol (C₂H₆O) in water is sometimes used as a disinfectant. 1.00 L of this solution contains 553 g of ethanol and 335 g of water. What is the molality of the ethanol in this solution?