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Exam 4-solutions - Version 349 Exam 4 sutclie(51045 This...

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Version 349 – Exam 4 – sutcliffe – (51045) 1 This print-out should have 26 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0points For a certain 3 rd order reaction, k = 2 . 35 × 10 4 M x · s y . What would be the values of x and y, respectively? 1. -2, -1 correct 2. 3, -1 3. 1, -3 4. -1, -2 5. -3, -1 6. 2, 1 Explanation: Units of M 2 · s 1 would correspond to a 3 rd order reaction. 002 10.0points In the electrolytic refining of copper, the pure copper 1. serves as the anode. 2. is electroplated onto the anode. 3. serves as the positive electrode. 4. remains oxidized in solution. 5. is electroplated onto the cathode. cor- rect Explanation: 003 10.0points A non-steroidal anti-inflammatory drug is me- tabolized with a first-order rate constant of 3.25 day 1 . What is the half-life for the metabolism reaction? 1. 0.213 day correct 2. 2.25 day 3. 1.63 day 4. 0.308 day Explanation: 004 10.0points The rate of formation of NO 2 (g) in the reac- tion 2 N 2 O 5 (g) 4 NO 2 (g) + O 2 (g) is 5 . 78 (mol NO 2 ) / L / s. What is the rate at which N 2 O 5 decomposes? 1. 5 . 78 (mol N 2 O 5 ) / L / s 2. 2 . 89 (mol N 2 O 5 ) / L / s correct 3. 0 . 723 (mol N 2 O 5 ) / L / s 4. 11 . 6 (mol N 2 O 5 ) / L / s 5. 1 . 45 (mol N 2 O 5 ) / L / s Explanation: 005 10.0points NOTE: This is your BONUS question. Metallic Zn dissolves in an HCl solution and gives off H 2 (g) but Ni does not. Which statement is true? 1. Zn 2+ is a better oxidizing agent than Ni 2+ . 2. Ni is more easily reduced than Zn. 3. Ni is a better reducing agent than Zn. 4. Zn is more easily oxidized than H 2 . cor- rect 5. Zn is a better oxidizing agent than H + . Explanation: 006 10.0points
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Version 349 – Exam 4 – sutcliffe – (51045) 2 The overall reaction for the discharge of a nickel/cadmium cell is Cd + NiO 2 + 2 H 2 O Cd(OH) 2 + Ni(OH) 2 Which of the following statements is true? 1. Insoluble Cd(OH) 2 is deposited on the anode. correct 2. The nickel is oxidized during this reac- tion. 3. It is impossible to recharge a nickel/cadmium cell. 4. Cadmium metal loses 2 electrons and is converted to Cd 2+ at the cathode. Explanation: Looking at the reaction above, Cd Cd 2+ + 2 e is an oxidation reaction that will occur at the anode. The nickel is not oxidized because we have shown that Cd is being oxidized. Nickel/cadmium batteries are rechargable. Insoluble CD(OH) 2 is deposited on the an- ode since Cd is oxidized at the anode. 007 10.0points The aluminum-air battery is being consid- ered for use in automobiles. In this battery, aluminum metal undergoes oxidation to Al 3+ ions and forms Al(OH) 3 . O 2 from the air undergoes reduction to OH ions. Which half-reaction occurs at the anode? 1. reaction of Al 3+ ions with hydroxide ions to produce Al(OH) 3 2. capturing O 2 from the air so that it may form the OH ions 3. formation of OH ions from O 2 4. formation of Al 3+ ions from aluminum correct Explanation: Oxidation occurs at the anode. The oxida- tion process is Al Al 3+ + e 008 10.0points For the cell diagram Pt | H 2 (g) | H + (aq) || Co 3+ (aq) , Co 2+ (aq) | Pt what reaction occurs at the cathode?
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