Chapter 19 - Chapter 19 Electrochemistry I Redox Reactions...

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Chapter 19: Electrochemistry I. Redox Reactions a. e - transfer b. Oxidation = when oxidation number increases (lose an electron) c. Reduction = when oxidation number decreases (gain electrons) d. Ca (s) + 2HCl (aq) CaCl 2(aq) + H 2(g) e. 0 +2 Calcium – oxidized f. +1 0 Hydrogen- reduced II. Electrolytic Cell a. Uses an electric current to drive a non-spontaneous reaction b. Electrolysis c. Make certain chemicals III. Galvanic Cell a. Spontaneous reaction that generates electric current (voltage) b. Batteries and fuel cells c. G°=-nFE° i. F/n= constant ii. E = voltage d. Zn (s) + Cu 2+ (aq) Zn 2+ (aq) + Cu (s) , 1.08 V, exothermic e. Cu solid is cathode (+) and Zn solid is anode (-) f. Zn Zn 2+ + e - , oxidation g. Cu 2+ + e - Cu, reduction h. e - flows through wire useful work i. Flow from – electrode to + electrode (anode to cathode) ii. Formed by oxidation 1. Anode = oxidation iii. Consume by reduction 1. Cathode = reduction i. Polarities arise because ions of that charge flow to it i. Cations go to + terminal (making it +) = cathode ii. Anions go to – terminal (making it -) = anode iii. Flow via salt bridge j. Properties of ½ cells i. ONE element undergoes change in oxidation state (#) ii. Have to include e - iii. Reduction: e - on left side iv. Oxidation: e - on right side v. ½ cell must contain active chemicals in the ½ reaction 1. no more, no less vi. Fe 3+ (aq) + e - Fe 2+ (aq) 1. Inert electrode a. Not take part in reaction b. Platinum, Graphite 2. Solution a. Need Fe 2+ AND Fe 3+ in solution
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vii.MnO 4 - + 8H + + 5e - Mn 2+ + 4H 2 O
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This note was uploaded on 01/27/2011 for the course CHEM 0120 taught by Professor Golde during the Spring '07 term at Pittsburgh.

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Chapter 19 - Chapter 19 Electrochemistry I Redox Reactions...

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