110221 - Electrochemistry (Chapter 7 sel. p.)...

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1 CHM3400 - Lecture 19 Feb 21 Electrochemistry (Chapter 7 sel. p.) Electrochemical cells Standard reduction potential Nernst equation Fuel cells Biological oxidations
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2 Redox chemistry CuSO 4 solution If add Zn metal to this solution. What happens? Zn(s) + Cu 2+ (aq) Zn 2+ (aq) + Cu(s) Blue color fades away
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3 Electrochemical cells Galvanic or voltaic cell Zn(s)|ZnSO 4 (1.00 M)| |CuSO 4 (1.00 M)|Cu(s) anode cathode Oxidation at anode Reduction at cathode Zn(s) Zn 2+ (aq) + 2e - Cu 2+ (aq) + 2e - Cu(s) What is the electromotive force (i.e., electrical potential) associated with this cell set-up? What is the role of the salt bridge?
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4 Standard hydrogen electrode (SHE) H + (1 M) + e - ½ H 2 (1 bar) E o = 0 V For historical reasons, this is the reference potential against which all other half-cell potentials are defined Arbitrarily:
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5 Electromotive force (EMF) Standard reduction potentials E o = E o cathode -E o anode For: Zn(s) Zn 2+ (aq) + 2e - Cu 2+ (aq) + 2e - Cu(s) E o = 0.342 (-0.762) = +1.104 V Reduction at cathode Oxidation at anode Why minus sign?
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This note was uploaded on 05/29/2011 for the course CHM 3400 taught by Professor Seabra during the Spring '08 term at University of Florida.

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110221 - Electrochemistry (Chapter 7 sel. p.)...

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