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DIRECTIONS: Write on the line at the right of each statement the letter preceding the word or expression that bestcompletes the statement.

1. Which of the following has components that are obviously different? (a) homogeneous mixture(b) solution (c) colloid (d) heterogeneous mixture

2. Types of mixtures are classified according to (a) color; (b) particle mass; (c) relative quantitiesof components; (d) particle size.

3. Molecules whose water solutions conduct current (a) dissociate in water; (b) ionize in water;(c) do not dissolve in water; (d) decompose in water.

4. In order to conduct electricity in water solutions, a particle must be (a) charged and mobile;(b) noncharged and mobile; (c) charged and nonmobile; (d) noncharged and nonmobile.

5. Which of the following mixtures contains particles that are in a dispersed phase and do notsettle out? (a) colloids (b) heterogeneous mixtures (c) solutions (d) suspensions

6. Colloids (a) are separable by filtration; (b) settle out on standing; (c) scatter light;(d) are obviously heterogeneous.

7. Which of the following does NOT increase the rate of dissolving of a solid in water?(a) raising the temperature (b) stirring (c) using large pieces of solid (d) crushing the solid

8. Raising the collision rate between solute and solvent (a) increases dissolving rate; (b) decreasesdissolving rate; (c) has no effect on dissolving rate; (d) can have any of the above effects.

9. If the amount of dissolved solute in a solution is greater than the amount that can

permanently remain in solution, the solution is (a) saturated; (b) unsaturated;(c) supersaturated; (d) dilute.

10. Which of the following is likely to release crystals of solid from solution, if undisturbed?(a) an unsaturated solution (b) a supersaturated solution (c) a saturated solution(d) all of the above

11. In the expression "like dissolves like," the word "like" refers to similarity in molecular(a) mass; (b) size; (c) energy; (d) polarity.

12. Hydrocarbons tend to be (a) polar; (b) nonpolar; (c) ionic; (d) hydrogen-bonded.

13. When the energy released by the forming of solvent-solute attractions is greater than theenergy absorbed by overcoming solute-solute and solvent-solvent attractions, a dissolvingprocess (a) has a negative heat of solution; (b) has a positive heat of solution; (c) occursrapidly; (d) does not occur.

14. The dissolving of gases in liquids is generally (a) endothermic; (b) exothermic; (c) rapid;(d) impossible.

15. Henry's law relates (a) pressure to temperature; (b) pressure to gas-liquid solubility;(c) temperature to gas-liquid solubility; (d) pressure to liquid-solid solubility.

16. As temperature increases, solubility of gases in liquids (a) increases; (b) decreases;(c) can increase or decrease; (d) is not affected.

17. Which of the following is an expression of concentration? (a) molality (b) molarity(c) percent concentration by mass (d) all of the above

18. Percent concentration by mass equals (a) moles solute per liter solution;(b) moles solute per kilogram solvent; (c) moles solute per liter solvent;(d) grams solute per 100 g solution, times 100.

19. The symbol M stands for (a) volume; (b) molality; (c) percent concentration by mass;(d) molarity.

20. A saturated solution (a) is always concentrated; (b) is always dilute; (c) is neither concentratednor dilute; (d) may be either concentrated or dilute.

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Chapter 14 69

21. A concentration expressed in terms of which of the ~llowing can change with temperature?(a) molality (b) molarity (c) percent concentration by mass (d) all of the above

22. What effect does the presence of a nonvolatile solute have on liquid-solvent vapor pressure?(a) It raises it. (b) It lowers it. (c) It can either raise or lower it. (d) It has no effect on it.

23. A colligative property is one that depends on (a) the number of solute particles but not theiridentity; (b) the identity of solute particles but not their number; (c) both the number andidentity of solute particles; (d) neither the number nor the identity of solute particles.

24. Which of the following correctly expresses freezing-point depression?(a) Mr = Kdm (b) Mr = m/Kr (c) Mr = Krm (d) Mr = KrM

25. The units of Kb are (a) Co; (b) mol solute/kg water; (c) CO/molal;(d) molal/Co.

26. The symbol for freezing point depression is (a) Kb; (b) Kr; (c) Mr; (d) m.

27. Colligative properties can be used to determine solute molar mass because they(a) are constant; (b) depend only on the number of solute particles; (c) depend only on thenumber of solvent particles; (d) depend only on the identity of the solute.

28. Solute molality can be determined by measuring (a) either boiling-point elevation orfreezing-point depression; (b) neither boiling-point elevation nor freezing-point depression;(c) boiling-point elevation but not freezing-point depression; (d) freezing-point depression butnot boiling-point elevation.

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DIRECTIONS: Write the answer to questions 29-35 on the line to the right, and show your work in the spaceprovided.

29. Exactly 15.0 g of a substance can be dissolved in 150.0 g of water. What is the solubility ofthe substance, in grams per hundred grams of water?

30. The solubility of a substance is 12.0 g per 100. g water at 20.0 DC,and is 18.0 g per100. g water at 60.0 DC.How many grams of the substance can crystallize from a saturatedsolution that contains 200. g water at 60.0 DCif the solution is cooled to 20.0 DC?

31. What mass of water must be used to make a 1.35-m solution that contains 8.20 mol NaOH?

32. What is the value of Kb for a solvent, given that its boiling point is varied by 2.4 Cowhen thesolute concentration is 3.1 m?

33. What is the boiling point of a solution that contains 18.7 g of a solute of molar mass40.0 g/mol dissolved in 112 g water?

34. What is the molar mass of a solute, if dissolving 3.11 g of the solute in 38 g water produces asolution whose boiling point is elevated by 1.00 CO?

35. In order to determine the molar mass of a compound that has the empirical formula C2H30,

0.64 g of the compound was dissolved in 50.0 g of water. The freezing-point depression of theresulting solution was - 0.277 Co.What are the molar mass and empirical formula of thecompound?

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DIRECTIONS: Write on the line at the right of each statement the word or expression that best completes themeaning when substituted for the corresponding number.

36. The ~ is the substance that is dissolved in a homogeneous mixture. 36

37. When a solute dissolves and re-crystallizes at the same rate, the solution is at ~ . 37

38. A substance is likely to be ~ if it is not soluble in a polar solvent. 38

39. Changes in pressure have a large effect on the solubilities of ~ in liquids. 39

40. Pressure is related to ~ in Henry's law. 40

70 Chapter 14 SolutionsHRW material copyrighted under notice appearing earlier in this work

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DIRECTIONS: Write on the line at the right of each statement the letter preceding the word or expression that bestcompletes the statement.

1. Any substance whose water solution conducts electricity is a(n) (a) nonpolar substance;(b) covalent substance; (c) nonelectrolyte; (d) electrolyte.

2. In the solution process of an ionic compound, which of the following plays an important role?(a) the solvent only (b) both the ions and the solvent (c) the ions only (cl) neither the ions northe solvent

3. If water is evaporated from a solution of hydrated ions, (a) water molecules are alwaysincorporated into the resulting solid; (b) water molecules mayor may not be incorporated intothe resulting solid, depending on the substance; (c) water molecules are never incorporatedinto the resulting solid; (d) the original solute decomposes.

4. The right side of the uncompleted hydration equilibrium equation Li+(aq) + n H20 (e) ~ shouldbe (a) Li(aq) + [n H20(e)]+; (b) Li -(aq) + [n H20(e)j2+; (c) [Li+(H20)n ](aq); (d) [Li(H20)n] +(aq).

5. Water is a good solvent for ionic compounds because of (a) strong solute-solvent interactions;(b) strong solute-solute interactions; (c) the fact that water expands as it freezes; (d) thetransparency of water.

6. When separated ions become surrounded by water molecules, energy (a) is always absorbed;(b) is always released; (c) may be absorbed or released; (d) makes the water denser.

7. How many ions are produced by each formula unit of solid in a dissociation? (a) zero (b) one(c) two (d) two or more

8. Compounds are generally referred to as "slightly soluble" if the amount of them that can bedissolved in 100 g of water is (a) less than 0.1 g; (b) 0.1 g to 1 g; (c) 1 g to 10 g;(d) more than 10 g.

9. The formation of a solid when solutions of two ionic compounds are combined is called(a) hydration; (b) precipitation; (c) solvation; (d) dissociation.

10. A net ionic equation for a precipitation shows (a) spectator ions; (b) those ions that undergoreaction and the solid they form; (c) only those ions that undergo reaction;(d) only the solid formed.

11. Which of the following is NOT a net ionic equation? (a) Ag+ (aq) + Cl- (aq) ~ AgCl(s)(b) Fe2+(aq) + 2Cl-(aq) + 20H-(aq) ~ Fe(OHh(s) + 2Cl-(aq)(c) 3Ca2+(aq) + 2p3- (aq) ~ Ca3P2(s) (d) Cu2+(aq) + S2- (aq) ~ CuS(s)

12. Which ion is the spectator ion in the equation Cu2 + (aq) + Zn2 + (aq) + 2S2 - (aq) -+

CuS(s) + ZnS(s)? (a) Cu2 + (aq) (b) Zn2 + (aq) (c) S2- (aq) (d) none of the above

13. Which ions do not appear in the net ionic equation for the precipitation reaction involvingsolutions of KCl and Pb(N03h? (a) K+ (aq) and Cl- (aq) (b) Pb2+(aq)

(c) K+(aq) and NO; (aq) (d) Cl-(aq), K+(aq), and NO; (aq)

14. Molecular substances contain (a) ionic bonds; (b) polar covalent bonds; (c) nonpolar covalentbonds; (d) either polar covalent or nonpolar covalent bonds.

15. When a molecular substance ionizes in water, (a) charged particles are formed and the moreelectronegative atom becomes a negative ion; (b) charged particles are formed and the lesselectronegative atom becomes a negative ion; (c) no charged particles are formed;(d) ions that were already present are released.

16. An example of a hydrated proton is the (a) hydrogen ion; (b) hydronium ion;(c) water molecule; (d) hydrogen chloride molecule.

17. Proton hydration that involves the production of ions that have one H20 molecule per protonis (a) impossible; (b) equally likely in dilute and in concentrated solutions; (c) more likely inconcentrated than in dilute solutions; (d) more likely in dilute than in concentrated solutions.

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Chapter 15 73

18. Which of the following is a strong electrolyte (a) HCzH30z (b) HBr (c) HF (d) NH3

19. Which of the following is the largest solute component in an aqueous ammonia solution?(a) NH40H (b) NH: (c) NH3 (d) H30+

20. Which of the following describes the activity of a light on a conductivity apparatus used to testpure water? (a) shines brightly (b) shines moderately (c) shines dimly (d) does not shine

21. Tap water conducts electricity (a) less well than pure water; (b) as well as pure water; (c) betterthan pure water, because tap water contains dissolved ions; (d) better than pure water, becausetap water does not contain dissolved ions.

22. Electrolytes in solution conduct electricity because of (a) the conductivity of the water solvent;(b) the presence of molecules; (c) the presence of ions; (d) their nonpolarity.

23. Compared to a O.OI-m sugar solution, a O.OI-m MgCh solution has (a) the same freezing-pointdepression; (b) about twice the freezing-point depression; (c) about three times the freezing­point depression; (d) about four times the freezing-point depression.

24. As electrolyte concentration decreases, freezing-point depression (a) approaches the valuecalculated by assuming complete ionization; (b) gets further from the value calculated byassuming complete ionization; (c) remains exactly equal to the value calculated by assumingcomplete ionization; (d) remains equally far from the value calculated by assuming completeionization.

25. Actual freezing-point depressions of electrolyte solutions are slightly less than those calculated,because of (a) ion repulsion; (b) more complete ionization than expected; (c) ion attraction;(d) higher than expected effective concentration.

26. Compared to the freezing-point depression for a solution of an electrolyte that dissociates intoa 3+ and a 3- ion, the freezing-point depression for an equally concentrated solution of anelectrolyte that dissociates into a 1+ and a 1- ion is likely to be (a) the same; (b) slightly less;(c) much less; (d) greater.

27. The approximate freezing-point depression of a 0.020-m aqueous NaBr solution is(a) - 0.0093 Co; (b) - 0.019 Co; (c) - 0.037 Co; (d) - 0.074 Co

DIRECTIONS: Questions 28 and 29 refer to the following table.

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Solubility of Salts

1. Common sodium, potassium, and ammonium compounds are soluble in water.

2. Common nitrates, acetates, and chlorates are soluble.

3. Common chlorides are soluble except silver, mercury(I), and lead. [Lead(ll) chloride issoluble in hot water.]

4. Common sulfates are soluble except calcium, barium, strontium, and lead.

5. Common carbonates, phosphates, and silicates are insoluble except sodium,potassium, and ammonium.

6. Common sulfides are insoluble except calcium, barium, strontium, magnesium,sodium, potassium, and ammonium.

28. Determine which of the following combinations of solutions will produce a precipitate.(a) KCI and Ca(N03h (b) AgN03 and NaN03 (c) NaOH and FeCh (d) Ca(N03h and CuCh

29. Determine which of the following combinations of solutions will produce a precipitate.(a) KOH and NH4Cl (b) Fe(N03b and KCI (c) AgN03 and KCI (d) NH4Cl and NaZS04

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74 Chapter 15 Ions In Aqueous SolutionsHRW material copyrighted under notice appearing earlier in this work.