CH302 Homework 9-solutions

CH302 Homework 9-solutions - Bodet (ngb299) Homework 9...

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Bodet (ngb299) – Homework 9 – sutclife – (51630) 1 This print-out should have 24 questions. Multiple-choice questions may continue on the next column or page – Fnd all choices be±ore answering. ANOTEONCELLD IAGRAMS :Wh en the diagram is more complex than A | B || C | D then you should just assume everything on the LE²T o± the || is ±or the ANODIC re- action, and everything on the RIGHT o± the || is the CATHODIC reaction. A | indicates ap h a s eb ou n d a r y . Ac omm ao ± t e ns e p a - rates two species that are both in the same phase. ²ind a reduction hal± reaction in ta- ble 11.1 (Appendix table 5.5 is the same) that includes all o± the items in your anodic reac- tion, then Fnd one that includes everything in the cathodic reaction. Use these to write down your two hal± reactions and calculate your standard cell potential. I± Pt is listed on the ±ar le±t or right it is just an inert electrode, ignore it. Remember you have written a lot o± K’s in the last two chapters. I± you can Fnd two redox couples that will combine to ±orm the reaction your K is ±or, then you can calculate K! 001 10.0 points In a galvanic cell, 1. electrical energy is used to reverse spon- taneous chemical reactions. 2. oxidation and reduction take place at the same time but at diferent electrodes. cor- rect 3. oxidation takes place at the cathode. 4. electrolytes are added to carry electrons between electrodes. Explanation: The reaction in a galvanic cell is sponta- neous and does not need to be driven by a battery. Both reduction and oxidation occur. 002 10.0 points Zinc Copper 1 . 10 V V Voltmeter e - e - 1MZn 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 solid zinc electrode correct 3. The Zn 2+ (aq) ions in the 1 M solution 4. The Cu 2+ (aq) ions in the 1 M solution Explanation: Zn(s) + Cu 2+ (aq) Zn 2+ (aq) + Cu(s) Oxidation occurs at the anode. In this cell the oxidation hal± reaction is Zn(s) Zn 2+ (aq) + 2 e - Zn atoms in the solid Zn electrode are oxidized to Zn 2+ ions; the electrode slowly erodes. 003 10.0 points The standard potential o± the cell Ag(s) | AgCl(s) | Cl - (aq) || Cu 2+ (aq) | Cu(s) is +0.12 V at 25 C. I± the standard potential o± the Cu 2+ | Cu couple is +0.34 V, calculate the standard potential o± the AgCl | Ag,Cl - couple. 1. - 0.46 V 2. - 0.22 V 3. +0.22V correct
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Bodet (ngb299) – Homework 9 – sutclife – (51630) 2 4. - 0.12 V 5. +0.46V Explanation: 004 10.0 points IF the standard potentials For the cou- ples ±e 3+ | ±e 2+ ,M n O 2 - 4 , H + | Mn 2+ , H 2 O, Zn 2+ | Zn, V 3+ | V 2+ ,andBr 2 | Br - are +0.77, +1.51, - 0.76, - 0.26, and +1.09 V, respec- tively, which is the strongest oxidizing agent?
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This note was uploaded on 10/06/2011 for the course CH 302 taught by Professor Holcombe during the Spring '07 term at University of Texas at Austin.

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CH302 Homework 9-solutions - Bodet (ngb299) Homework 9...

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