Kaplan MCAT General Chemistry Review

7. A 0.01 M solution of a nonelectrolyte has an osmotic pressure of 15.0 mm Hg. What is the osmotic pressure of a 0.02 M solution of Mg(NO₃)₂? The temperature of both solutions is the same.

A. 7.5 mm Hg

B. 30 mm Hg

C. 45 mm Hg

D. 90 mm Hg

8. One hundred grams of sugar are dissolved in a cup of hot water at 80°C. The cup of water contains 300.00 mL of water. What is the mass percentage of sugar in the resulting solution? (Sugar = C₁₂H₂₂O₁₁, density of water at 80°C = 0.975 g/mL.)

A. 25.0%

B. 25.5%

C. 33.3%

D. 34.2%

9. Which of the following combinations of liquids would be expected to have a vapor pressure higher than the vapor pressure that would be predicted by Raoult’s law?

A. Ethanol and hexane

B. Acetone and water

C. Isopropanol and methanol

D. Nitric acid and water

10. The salt KCl is dissolved in a beaker of water that you are holding. You can feel the solution cool as the KCl dissolves. From this observation you conclude that

A. S°_soln is large enough to overcome the unfavorable H°_soln.

B. KCl is mostly insoluble in water.

C. S°_soln must be negative when KCl dissolves.

D. Boiling point elevation will occur in this solution.

11. Which of the following will give the greatest increase in the boiling point of water when it is dissolved in 1.00 kg H₂O?

A. 0.46 mol calcium sulfate

B. 0.54 mol iron (III) nitrate

C. 1.09 mol acetic acid

D. 1.11 mol sucrose

12. At sea level and 25°C, the solubility of oxygen gas in water is 1.25 × 10^-3 M. In a city in the United States that lies high above sea level, the atmospheric pressure is 0.800 atm. What is the solubility of oxygen in water in this city?

A. 1.05 × 10^-3 M

B. 1.56 × 10^-3 M

C. 1.00 × 10^-3 M

D. 1.25 × 10^-3 M

13. Lead is a dangerous element that exists in the environment in large quantities due to man-made pollution. Lead poisoning has many symptoms, including mental retardation in children. If a body of water is polluted with lead ions at 30 ppb (parts per billion), what is the concentration of lead in molarity? (Density of water is 1 g/mL, ppb equals grams per 10⁹ grams of solution.)

A. 6.2 × 10^-7 M Pb²⁺

B. 1.4 × 10^-10 M Pb²⁺

C. 1.4 × 10^-7 M Pb²⁺

D. 6.2 × 10^-6 M Pb²⁺

14. Which of the following is/are correct?

I. NaF is an electrolyte.

II. Glucose is a nonelectrolyte.

III. CH₃OH is a weak electrolyte.

IV. CH₃CH₂COOH is a weak electrolyte.

A. I, III, and IV only

B. I and II only

C. II, and IV only

D. I, II, and IV only

15. Which one of the following is not a colligative property?

A. Boiling point elevation

B. Vapor pressure of a mixture

C. Osmotic pressure

D. Entropy of dissolution

16. The following equilibrium exists when AgBr is in solution:

Calculate the solubility of AgBr in g/L in a solution of 0.0010 M NaBr.

A. 7.7 × 10^-13 g/L

B. 8.3 × 10^-12 g/L

C. 7.7 × 10^-10 g/L

D. 8.3 × 10^-8 g/L

17. When ammonia, NH₃, is a solvent, complex ions can form. For example, dissolving AgCl in NH₃ will result in the complex ion Ag(NH₃)²⁺. What effect would you expect the formation of complex ions to have on the solubility of a compound like AgCl in NH₃?

A. The solubility of AgCl will increase, because complex ion formation will cause more ions to exist in solution, which interact with AgCl to cause it to dissociate.

B. The solubility of AgCl will increase, because complex ion formation will consume Ag⁺ molecules and cause the equilibrium to shift away from solid AgCl.

C. The solubility of AgCl will decrease, because Ag⁺ ions are in complexes and the Ag⁺ ions that are not complexed will want to associate with Cl^- to form solid AgCl.

D. The solubility of AgCl will decrease, because complex ion formation will consume Ag⁺ molecules and cause the equilibrium to shift toward the solid AgCl.

18. Detergents are compounds that are dissolved in water. However, they are also able to dissolve hydrophobic stains, such as oil and grease in clothing and other fabrics. How are these compounds able to fulfill both hydrophilic and hydrophobic functions?

A. They contain a hydrophobic core molecule encased in a hydrophilic shell.

B. They can ionize into two parts; one part is ionic, and the other part is hydrophobic.

C. They have two states; in water they are ionic, and in hydrophobic solvents they form nonpolar ring structures.

D. They have two functionally distinct parts; one side is a hydrophobic chain, and the other end is polar and ionic.

Small Group Questions

1. How does the presence of common ions in solution affect K_sp? I.P. (Q_sp)?

2. Discuss the circumstances that permit solvation. What forces are involved?

Explanations to Practice Questions

1. A