Sample Questions - Chapter 14

Solutions

Examples of
Multiple Choice Questions

Consider the three statements below. Which statement(s) is(are) true?; 1. Hydration is a special case of solvation in which the solvent is water.; 2. The oxygen end of water molecules is attracted toward Ca²⁺ ions.; 3. The hydrogen end of water molecules is attracted toward Cl^- ions.; (a) 1 only; (b) 2 only; (c) 3 only; (d) 1 and 2 only; (e) 1, 2, and 3
2.: Consider the following pairs of liquids. Which pairs are miscible?; 1. benzene, C₆H₆, and hexane, C₆H₁₂; 2. water and methanol, CH₃OH; 3. water and hexane; (a) 1, 2 only; (b) 2 only; (c) 1 only; (d) 1, 2, 3; (e) 2, 3 only
3.: Calculate the molality of a solution that contains 51.2 g of naphthalene, C₁₀H₈, in 500 mL of carbon tetrachloride. The density of CCl₄ is 1.60 g/mL.; (a) 0.250 m; (b) 0.500 m; (c) 0.750 m; (d) 0.840 m; (e) 1.69 m
4.: What is the molality of a solution labeled "8.6% glucose (C₆H₁₂O₆) by weight?" (Note: If the question does not give the solvent, assume it is water.); (a) 0.26 m; (b) 0.34 m; (c) 0.44 m; (d) 0.52 m; (e) 0.67 m
5.: Calculate the mole fraction of C₂H₅OH in a solution that contains 46 grams of ethanol, C₂H₅OH, and 64 grams of methanol, CH₃OH.; (a) 1/3; (b) 0.42; (c) 1/2; (d) 2/3; (e) none of these
6.: Which observation(s) reflect(s) colligative properties?; (I) A 0.5 m NaBr solution has a higher vapor pressure than a 0.5 m BaCl₂ solution.; (II) A 0.5 m NaOH solution freezes at a lower temperature than pure water.; (III) Pure water freezes at a higher temperature than pure methanol.; (a) only I; (b) only II; (c) only III; (d) I and II; (e) I and III
7.: The vapor pressure of pure water at 85^oC is 434 torr. What is the vapor pressure at 85^oC of a solution prepared from 100 mL of water (density 1.00 g/mL) and 150 g of diglyme, C₆H₁₄O₃, a nonvolatile substance?; (a) 361 torr; (b) 390 torr; (c) 425 torr; (d) 388 torr; (e) 317 torr
8.: The vapor pressure of a solution containing a nonvolatile solute is directly proportional to the; (a) molality of the solvent.; (b) osmotic pressure of the solute.; (c) molarity of the solvent.; (d) mole fraction of solvent.; (e) mole fraction of solute.
9.: If 4.27 grams of sucrose, C₁₂H₂₂O₁₁, are dissolved in 15.2 grams of water, what will be the boiling point of the resulting solution? (K_b for water = 0.512 ^oC/m) (Note: If the K_f and K_b are not given on the exam, you can find them on the back of the exam envelope.); (a) 101.64 ^oC; (b) 100.42 ^oC; (c) 99.626 ^oC; (d) 100.73 ^oC; (e) 101.42 ^oC
10.: What are the ideal van't Hoff factors for the following compounds: Ba(OH)₂, C₆H₁₂O₆, K₃PO₄, HNO₃ ?; (a) 1, 1, 1, 1; (b) 2, 1, 2, 2; (c) 3, 1, 4, 2; (d) 6, 3, 5, 5; (e) none of the above
11.: Calculate the approximate initial boiling point (in ^oC) of a solution of 285 g of magnesium chloride in 2.0 kg of water. (Assume complete dissociation of the salt.); (a) 103.1 ^oC; (b) 101.6 ^oC; (c) 102.3 ^oC; (d) 100.8 ^oC; (e) 104.8 ^oC
12.: A solution made by dissolving 9.81 g of a nonvolatile nonelectrolyte in 90.0 g of water boiled at 100.37 ^oC at 760 mm Hg. What is the approximate molecular weight of the substance? (For water, K_b = 0.51 ^oC/m); (a) 240 g/mol; (b) 150 g/mol; (c) 79 g/mol; (d) 61 g/mol; (e) 34 g/mol
13.: What is the freezing point of an aqueous 1.00 m NaCl solution? (K_f = 1.86 ^oC/m) (Assume complete dissociation of the salt.); (a) -1.86 ^oC; (b) +1.86 ^oC; (c) -3.72 ^oC; (d) -0.93 ^oC; (e) 0.0 ^oC
14.: A 17.3 mg sample of an organic compound (a non-electrolyte) was ground up with 420 mg of camphor to form a homogeneous mixture melting at 170.0 ^oC. What is the apparent formula weight of the organic compound? (K_f of camphor = 37.7 ^oC/m, m.p. of camphor = 178.4 ^oC) (Note: This is a freezing point depression problem - note the K_f of camphor - camphor is the solvent.); (a) 353 g/mol; (b) 285 g/mol; (c) 231 g/mol; (d) 185 g/mol; (e) 166 g/mol
15.: Calculate the osmotic pressure associated with 50.0 g of an enzyme of molecular weight 98,000 g/mol dissolved in water to give 2600 mL of solution at 30.0 ^oC.; (a) 0.484 torr; (b) 1.68 torr; (c) 1.96 torr; (d) 2.48 torr; (e) 3.71 torr
16.: A 250 mL solution containing 21.4 g of a polymer in toluene had an osmotic pressure of 0.055 atm at 27 ^oC. What is the apparent formula weight of the polymer?; (a) 15,000 g/mol; (b) 18,000 g/mol; (c) 26,000 g/mol; (d) 32,000 g/mol; (e) 38,000 g/mol

Answers:

1. (e) 2. (a) 3. (b) 4. (d) 5. (a) 6. (d) 7. (a) 8. (d) 9. (b) 10. (c) 11. (c) 12. (b) 13. (c) 14. (d) 15. (e) 16. (e)

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