Feb. 24, 2000 Page 1. CHM 1046 Practice Exam 2 Spring 2000 Palmer Graves, Instructor MULTIPLE CHOICE. Section 13.3 The Equilibrium Constant K p

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1 Feb. 24, 2000 Page 1 MULTIPLE CHOICE Section 13.3 The Equilibrium Constant K p 1. Phosphorus pentachloride decomposes to phosphorus trichloride and chlorine gas at elevated temperatures by the following reaction: PCl (g) PCl (g) + Cl (g). If K c = 1.8 at 250 C, what is the value of K p at the same temperature? a) 4.2 x 10 b) 8.8 x 10 c) 65 d) 77 Section 13.4 Heterogeneous Equilibria 2. For the reaction, A(g) + 2 B(g) 2 C(g), K c = 1 x 10 at 25 C. Which of the following statements is true? a) n = +1 b) The concentration of the products is greater than the concentration of the reactants. c) The reaction is favored in the reverse direction. d) The value of K p will be larger than the value for K c. 3. Which statement is true for a reaction with K c equal to 2.43 x 10? a) Increasing the temperature will not change the value of K c. b) There are appreciable concentrations of both reactants and products. c) The reaction proceeds hardly at all towards completion. d) The reaction proceeds nearly all the way to completion. Section 13.5 Using the Equilibrium Constant 4. For the reaction: 4 HCl(g) + O (g) 2 Cl (g) + 2 H O(l), the equilibrium constant is at 400 K. If the reaction quotient is 0.100, which of the following statements is not correct? a) [HCl] will increase. b) [O ] will increase. c) [Cl ] will decrease. d) [H O] will increase. 5. The equilibrium constant, K p, equals 3.40 at 25 C for the isomerization reaction: cis-2-butene trans-2-butene. If a flask initially contains 1.00 atm of each gas, what direction will the reaction shift to reach equilibrium? a) It will shift left. b) It will shift right. c) The reaction is already at equilibrium. d) The reaction is at equilibrium initially and then will shift right.

2 Feb. 24, 2000 Page 2 Sections Altering an Equilibrium Mixture: Changes in Concentration, Pressure, Volume, and Temperature 6. Which change in the system will drive equilibrium to the left in the reaction below? N O (g) NO (g) + NO (g) a) Decrease the amount of NO. b) Increase the amount of N O. c) Increase the pressure. d) Increase the volume. 7. Iron oxide ores are reduced to iron metal by exothermic reaction with carbon monoxide: FeO(s) + CO(g) Fe(s) + CO (g). Which of the following changes in condition will cause the equilibrium to shift to the right? a) Add FeO. b) Add CO. c) Add CO. d) Raise the temperature. Section 15.1 Acid-Base Concepts: The Br nsted-lowry Theory 8. An Arrhenius acid is best defined as a a) hydroxide donor. b) proton acceptor. c) substance that dissociates in water to produce aqueous hydrogen ions. d) substance that dissociates in water to produce aqueous hydroxide ions. 9. A Br nsted-lowry acid is best defined as a substance that can a) accept a hydroxide ion. b) donate a hydroxide ion. c) accept a proton. d) donate a proton. 10. What are the conjugate acid-base pairs in the following chemical reaction NH (aq) + H O(l) NH (aq) + OH (aq)? a) NH, H O and NH, OH b) NH, NH and H O, OH c) NH, OH and H O, NH d) NH and NH Sections Hydrated Protons and Dissociation of Water 11. A solution with a hydrogen ion concentration of 3.25 x 10 M is and has a hydroxide concentration of. a) acidic, 3.08 x 10 M b) acidic, 3.08 x 10 M c) basic, 3.08 x 10 M d) basic, 3.08 x 10 M

3 Feb. 24, 2000 Page 3 Section 15.5 The ph Scale 12. What is the hydronium ion concentration of an acid rain sample that has a ph of 3.15? a) 1.41 x 10 M b) 7.08 x 10 M c) 3.15 M d) M 13. What is the hydroxide ion concentration of a lye solution that has a ph of 11.20? a) 6.31 x 10 M b) 2.00 x 10 M c) 1.58 x 10 M d) M Section 15.7 The ph in Solutions of Strong Acids and Strong Bases 14. What is the ph of a solution prepared by diluting ml of M HCl to a volume of ml? a) 1.00 b) 1.60 c) 2.00 d) What is the ph of a solution made by mixing ml of M Ca(OH) with ml of M NaOH? Assume that the volumes are additive. a) b) c) d) Section 15.8 Equilibria Solutions of Weak Acids 16. Determine the acid dissociation constant for a 0.10 M acetic acid solution that has a ph of Acetic acid is a weak monoprotic acid and the equilibrium equation of interest is CH COOH(aq) + H O(l) H O (aq) + CH CO (aq). a) 1.3 x 10 b) 1.3 x 10 c) 1.8 x 10 d) 1.8 x Determine the acid dissociation constant for a M formic acid solution that has a ph of Formic acid is a weak monoprotic acid and the equilibrium equation of interest is HCOOH(aq) + H O(l) H O (aq) + HCO (aq). a) 1.8 x 10 b) 1.8 x 10 c) 3.6 x 10 d) 3.6 x 10

4 Feb. 24, 2000 Page 4 Section 15.9 Calculating Equilibrium Concentrations in Solutions of Weak Acids 18. What is the hydronium ion concentration of a M hypochlorous acid solution with a K a = 3.5 x 10? The equation of interest is HOCl(aq) + H O(l) H O (aq) + OCl (aq) a) 1.9 x 10 b) 5.9 x 10 c) 1.9 x 10 d) 5.9 x 10 Section Percent Dissociation in Solutions of Weak Acids 19. What is the percent dissociation of a benzoic acid solution with ph = 2.59? The acid dissociation constant for this monoprotic acid is 6.5 x 10. a) 0.50% b) 1.5% c) 2.5% d) 3.5% Section Equilibria in Solutions of Weak Bases 20. What is the ph of a 0.30 M pyridine solution that has a K b of 1.9 x 10 and the equilibrium equation of interest is C H N(aq) + H O(l) C H NH (aq) + OH (aq)? a) 4.62 b) 8.72 c) 9.38 d) Section Relation Between K a and K b 21. Methylamine CH NH, has a base dissociation constant of 3.7 x 10. What is the conjugate acid of methylamine and what is its acid dissociation constant? a) CH NH, 2.7 x 10 b) CH NH, 3.7 x 10 c) CH NH, 2.7 x 10 d) CH NH, 2.7 x 10 Section Acid-Base Properties of Salts 22. Which of the following species acts as a base in water? a) HSO b) LiClO c) MgO d) CH NH I

5 Feb. 24, 2000 Page Arrange the following 0.10 M aqueous solutions in order of increasing ph NaOH, HBr, NaCH CO, KBr, NH Br. a) HBr, KBr, NH Br, NaCH CO, NaOH b) NaOH, NaCH CO, NH Br, KBr, HBr c) NaOH, NaCH CO, KBr, NH Br, HBr d) HBr, NH Br, KBr, NaCH CO, NaOH 24. What is the ph of a M CH NH Cl solution if the K b for methylamine (CH NH ) is 3.7 x 10? a) 2.22 b) 5.79 c) d) Section Lewis Acids and Bases 25. Which one of the following is not considered to be a Lewis base? a) H O b) NH c) NH d) Cl (c) 1998 Prentice-Hall, Inc. All rights reserved.

6 ANSWER KEY FOR TEST UNTITLED Feb. 24, 2000 Page 1 1. d) 2. c) 3. c) 4. d) 5. b) 6. c) 7. b) 8. c) 9. d) 10. b) 11. b) 12. b) 13. c) 14. b) 15. b) Chapter: 13 QUESTION: 21 Chapter: 13 QUESTION: 36 Chapter: 13 QUESTION: 37 Chapter: 13 QUESTION: 38 Chapter: 13 QUESTION: 40 Chapter: 13 QUESTION: 68 Chapter: 13 QUESTION: 69 Chapter: 15 QUESTION: 2 Chapter: 15 QUESTION: 4 Chapter: 15 QUESTION: 10 Chapter: 15 QUESTION: 31 Chapter: 15 QUESTION: 39 Chapter: 15 QUESTION: 40 Chapter: 15 QUESTION: 49 Chapter: 15 QUESTION: 53

7 ANSWER KEY FOR TEST UNTITLED Feb. 24, 2000 Page c) 17. b) 18. d) 19. c) 20. c) 21. c) 22. c) 23. d) 24. b) 25. c) Chapter: 15 QUESTION: 57 Chapter: 15 QUESTION: 59 Chapter: 15 QUESTION: 61 Chapter: 15 QUESTION: 66 Chapter: 15 QUESTION: 78 Chapter: 15 QUESTION: 84 Chapter: 15 QUESTION: 88 Chapter: 15 QUESTION: 90 Chapter: 15 QUESTION: 95 Chapter: 15 QUESTION: 111 (c) 1998 Prentice-Hall, Inc. All rights reserved.