final - Version 286 – Final Exam – Holcombe –(52460...

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Version 286 – Final Exam – Holcombe – (52460) 1 This print-out should have 50 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points What is the rate law for the reaction A + B C ? The following data were collected. Exp [A] 0 [B] 0 Initial Rate 1 0.5 1.2 1 . 40 × 10 3 2 1.7 1.2 1 . 40 × 10 3 3 0.5 0.7 4 . 76 × 10 4 1. rate = 5 . 6 × 10 3 [A] 2 [B] 0 2. rate = 9 . 72 × 10 4 [A] 0 [B] 2 correct 3. rate = 1 . 94 × 10 3 [A] 0 [B] 2 4. rate = 2 . 33 × 10 3 [A] 0 [B] 2 5. rate = 4 . 67 × 10 3 [A] 2 [B] 1 Explanation: 002 10.0 points The solubility product constant of AgCl is 1 . 8 × 10 10 and that of AgBr is 3 . 3 × 10 13 . Solid AgNO 3 is slowly added to a solution containing 0.0010 M each of NaCl and NaBr. What concentration of Br would remain in solution when AgCl begins to precipitate? 1. 5 . 5 × 10 1 M 2. 1 . 8 × 10 6 M correct 3. 5 . 5 × 10 4 M 4. 1 . 8 × 10 4 M 5. 1 . 8 × 10 10 M Explanation: 003 10.0 points When we put sugar in water it melts. 1. False correct 2. True Explanation: Sugar dissolves in water and melts when its temperature is raised above its melting point. 004 10.0 points The equilibrium constant (dimensionless) for A B is 2. If the initial concentrations of A and B are each 1.0 M, what are the final concentra- tions of A and B respectively? 1. [A] = 0.67 M; [B] = 0.33 M 2. [A] = 1.00 M; [B] = 2.00 M 3. [A] = 0.67 M; [B] = 1.33 M correct 4. [A] = 0.50 M; [B] = 1.00 M 5. [A] = 1.00 M; [B] = 1.33 M Explanation: K = 2 [A] ini = 1 . 0 M [B] ini = 1 . 0 M Q = [B] [A] = 1 . 0 1 . 0 = 1 . 0 < K = 2 Therefore, the equilibrium moves to the right. A B(g) ini, M 1 . 0 1 . 0 Δ, M - x x eq, M 1 . 0 - x 1 . 0 + x K = [B] [A] = 2 1 . 0 + x 1 . 0 - x = 2 1 . 0 + x = 2 . 0 - 2 x x = 0 . 33 [A] = 1 . 0 - x = 0 . 67 M [B] = 1 . 0 + x = 1 . 33 M
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Version 286 – Final Exam – Holcombe – (52460) 2 005 10.0 points In a sample of pure water at 25 C, the ratio [H 3 O + ] [OH ] is equal to 1. 14.0 2. 7.0 3. 1.0 correct 4. 1 . 0 × 10 14 5. 1 . 0 × 10 7 Explanation: 2 H 2 O H 3 O + + OH let x = [H 3 O + ] = [OH ] , K w = [H 3 O + ][OH ] = x 2 = 10 14 x = 10 7 so [H 3 O + ] [OH ] = 10 7 10 7 = 1 006 10.0 points Consider the following pressure diagram for a binary liquid containing A and B. 0 1 x A 50 torr 90 torr A solution is mixed such that x A = 0 . 45. What is the vapor pressure of B? 1. 68 torr 2. 27 torr correct 3. 40 torr 4. 90 torr 5. 50 torr Explanation: 0 1 0 . 45 90 torr 27 torr 007 10.0 points Zinc Copper 1 . 10 V V Voltmeter e e 1 M Zn 2+ (aq) 1 M Cu 2+ (aq) Salt bridge to carry ions In this electrochemical cell, what is the an- ode? 1. The solid copper electrode 2. The Cu 2+ (aq) ions in the 1 M solution 3. The Zn 2+ (aq) ions in the 1 M solution 4. The solid zinc electrode correct Explanation: Zn(s) + Cu 2+ (aq) Zn 2+ (aq) + Cu(s) Oxidation occurs at the anode. In this cell the oxidation half reaction is Zn(s) Zn 2+ (aq) + 2 e
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Version 286 – Final Exam – Holcombe – (52460) 3 Zn atoms in the solid Zn electrode are oxidized to Zn 2+ ions; the electrode slowly erodes.
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