PRACTICE MULTIPLE CHOICE- Chapters 17&18

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1 PRACTICE MULTIPLE CHOICE- Chapters 17&18 1. What is the solubility product expression for Fe2(CO3)3? A) Ksp = [2Fe 3+ ][3CO3 2 ] B) Ksp = [2Fe 3+ ] 2 [3CO3 2 ] 3 C) Ksp = [Fe 2+ ] 2 [CO3 2 ] 3 D) Ksp = [Fe 3+ ] 2 [CO3 2 ] 3 E) Ksp = [2Fe 3+ ] 2 [CO3 2 ] 3 2. What is the solubility (in g/l) of calcium sulfate at 25 C? The solubility product constant for calcium sulfate is at 25 C. A) 0.67 g/l B) g/l C) 2.5 g/l D) g/l E) 4.8 g/l 3. The solubility of La(IO3)3 in a 0.89 M KIO3 solution is mol/l. Calculate Ksp for La(IO3)3. A) B) C) D) E) none of these 4. A M solution of MnSO4 is gradually made more basic by adding NaOH. At what ph will manganese(ii) hydroxide begin to precipitate? For Mn(OH)2, Ksp = A) 4.74 B) 9.48 C) 9.26 D) 4.52 E) If 200 ml of M AgNO3 is mixed with 200 ml of M NaI, what will occur? For AgI, Ksp = A) No precipitate will form. B) Silver(I) nitrate will precipitate. C) Silver(I) iodide will precipitate. D) Sodium nitrate will precipitate. E) Sodium iodide will precipitate. 6. The best explanation for the dissolution of ZnS in dilute HCl is that A) the zinc ion is amphoteric. B) the sulfide ion concentration is decreased by the formation of H2S. C) the solubility product of ZnCl2 is less than that of ZnS. D) the zinc ion concentration is decreased by the formation of a chloro complex. E) the sulfide ion concentration is decreased by oxidation to sulfur. 7. What is the best way to ensure complete precipitation of SnS from a saturated H2S solution?

2 A) Add a strong acid. B) Add a weak acid. C) Add a strong base. D) Add a weak base. E) Add more H2S. 8. Cyanide ion forms very stable complex ions with a variety of metal ions. What is the molar equilibrium concentration of uncomplexed Ag + (aq) in a solution that initially contains 1.3 mol of Ag(CN)2 per liter of solution. Kf for Ag(CN)2 is A) M B) M C) M D) M E) M 9. Given the following equilibrium constants, Zn(IO3)2 Ksp = Zn(NH3)4 2+ Kf = determine Kc for the dissolution of the sparingly soluble salt Zn(IO3)2 in aqueous ammonia (shown below). Zn(IO3)2(s) + 4NH3(aq) Zn(NH3)4 2+ (aq) + 2IO3 (aq) A) B) C) D) E) Assuming H and S are constant with respect to temperature, under what conditions will a chemical reaction be spontaneous at all temperatures? A) H = 0, and S is negative. B) S = 0, and H is positive. C) H is positive, and S is negative. D) H is negative, and S is positive. E) none of these 11. For which of the following reactions is S > 0 at 25 C? A) 2H2(g) + O2(g) 2H2O(g) B) 2ClBr(g) Cl2(g) + Br2(g) C) I2(g) I2(s) D) 2NO(g) + O2(g) 2NO2(g) E) NH4HS(s) NH3(g) + H2S(g) 12. What is S at 298 K for the following reaction?

3 CH4(g) + N2(g) HCN(g) + NH3(g); H = kj; G = kj at 298 K A) 2.0 J/K B) J/K C) J/K D) J/K E) 17 J/K 13. Given the following, determine G f at 298 K for PbO. Pb(s) + PbO2(s) 2PbO(s) ; G = kj at 298K Substance G f (kj/mol) at 298 K PbO(s)? PbO2(s) A) kj/mol B) 29.4 kj/mol C) kj/mol D) kj/mol E) 58.8 kj/mol 14. Which of the following is correct for the condensation of gaseous oxygen at 188 C? The normal boiling point of oxygen is 183 C. A) H > 0, S > 0, and G > 0. B) H < 0, S < 0, and G < 0. C) H < 0, S > 0, and G > 0. D) H > 0, S < 0, and G < 0. E) H = 0, S = 0, and G < For a reaction that has an equilibrium constant of , which of the following statements must be true? A) G is positive. B) S is positive. C) H is negative. D) G is negative. E) H is positive. 16. The standard free energy of formation of nitric oxide, NO, at K (roughly the temperature in an automobile engine during ignition) is 78.4 kj/mol. Calculate the equilibrium constant for the reaction 2NO(g) at K. (R = 8.31 J/(K mol)) A) B) C) 15 D)

4 E) Consider the following reaction: 2C(s) + 3H2(g) C2H6(g); H = kj; S = J/K at 298 K What is the equilibrium constant at 298 K for this reaction? A) B) C) D) E) What is G at K for the following reaction? Mg(s) + H2O(g) MgO(s) + H2(g) Substance H f (kj/mol) at 298 K S (J/(mol K)) at 298 K Mg(s) H2O(g) MgO(s) H2(g) A) kj B) kj C) kj D) kj E) kj 19. For the reaction SrCO3(s) SrO(s) + O2(g) at 1 atm pressure, the values of H and S are both positive, and the process is spontaneous at high temperatures. Which of the following statements about this reaction is true? A) The reverse reaction is endothermic. B) The change in entropy is the driving force for the reaction. C) G at room temperature is negative. D) The process is exothermic at high temperatures and endothermic at room temperature. E) The reverse reaction is nonspontaneous at room temperature. 20. Condensation is a process for which A) G is negative at high temperature but positive at low temperature. B) H, S, and G are positive at all temperatures. C) G is positive when condensation occurs spontaneously. D) H and S are positive at all temperatures. E) H and S are negative at all temperatures.

5 PRACTICE MULTIPLE CHOICE- Chapters 17&18 Answer Section 1. ANS: D PTS: 1 DIF: easy REF: 17.1 OBJ: Write solubility product expressions. (Example 17.1) TOP: solubility solubility equilibria KEY: solubility product constant 2. ANS: A PTS: 1 DIF: easy REF: 17.1 OBJ: Calculate the solubility from Ksp. (Example 17.4) TOP: solubility solubility equilibria KEY: solubility product constant 3. ANS: D PTS: 1 DIF: moderate REF: 17.2 OBJ: Calculate the solubility of a slightly soluble salt in a solution of a common ion. (Example 17.5) TOP: solubility solubility equilibria KEY: solubility and the common-ion effect MSC: general chemistry 4. ANS: C PTS: 1 DIF: easy REF: 17.3 OBJ: Predict whether precipitation will occur (given ion concentrations). (Example 17.6) TOP: solubility solubility equilibria KEY: precipitation calculations criterion for precipitation 5. ANS: C PTS: 1 DIF: easy REF: 17.3 OBJ: Predict whether precipitation will occur (given solution volumes and concentrations). (Example 17.7) TOP: solubility solubility equilibria KEY: precipitation calculations criterion for precipitation 6. ANS: B PTS: 1 DIF: easy REF: 17.4 OBJ: Explain the qualitative effect of ph on solubility of a slightly soluble salt. TOP: solubility solubility equilibria KEY: effect of ph on solubility qualitative effect of ph 7. ANS: C PTS: 1 DIF: moderate REF: 17.4 OBJ: Explain the basis for the sulfide scheme to separate a mixture of metal ions. TOP: solubility applications of solubility equilibria 8. ANS: C PTS: 1 DIF: easy REF: 17.5 OBJ: Calculate the concentration of a metal ion in equilibrium with a complex ion. (Example 17.9) TOP: solubility complex ion equilibria 9. ANS: B PTS: 1 DIF: easy REF: 17.6 OBJ: Calculate the solubility of a slightly soluble ionic compound in a solution of the complex ion. (Example 17.11) TOP: solubility complex ion equilibria 10. ANS: D PTS: 1 DIF: easy REF: OBJ: Describe how deltah TdeltaS functions as a criterion of a spontaneous reaction. 11. ANS: E PTS: 1 DIF: easy REF: 18.3 OBJ: Predict the sign of the entropy change of a reaction. (Example 18.2) KEY: third law of thermodynamics entropy change for a reaction

6 12. ANS: E PTS: 1 DIF: easy REF: 18.4 OBJ: Calculate deltag from deltah and deltas. (Example 18.4) KEY: free energy standard free energy change 13. ANS: A PTS: 1 DIF: easy REF: 18.4 OBJ: Calculate deltag from standard free energies of formation. (Example 18.5) 14. ANS: B PTS: 1 DIF: moderate REF: 18.4 OBJ: State the rules for using deltag as a criterion for spontaneity. KEY: free energy spontaneity 15. ANS: A PTS: 1 DIF: easy REF: 18.6 OBJ: Relate the standard free-energy change to the thermodynamic equilibrium constant. KEY: thermodynamic equilibrium constant (K) 16. ANS: B PTS: 1 DIF: easy REF: 18.6 OBJ: Calculate K from the standard free-energy change (molecular equation). (Example 18.8) KEY: thermodynamic equilibrium constant (K) 17. ANS: A PTS: 1 DIF: moderate REF: 18.6 OBJ: Calculate K from the standard free-energy change (molecular equation). (Example 18.8) KEY: thermodynamic equilibrium constant (K) 18. ANS: C PTS: 1 DIF: moderate REF: 18.7 OBJ: Describe how deltag at a given temperature (deltag T) is approximately related to deltah and deltas at that temperature. KEY: temperature dependence of free energy calculation of free energy change at various temperatures 19. ANS: B PTS: 1 DIF: easy REF: 18.7 OBJ: Describe the how spontaneity or nonspontaneity of a reaction is related to each of the four possible choices of signs of deltah and deltas. KEY: temperature dependence of free energy spontaneity and temperature change 20. ANS: E PTS: 1 DIF: moderate REF: 18.7 OBJ: Describe the how spontaneity or nonspontaneity of a reaction is related to each of the four possible choices of signs of deltah and deltas. KEY: temperature dependence of free energy spontaneity and temperature change