12-2-08[lecture22]jl

12-2-08[lecture22]jl - 2 (s) + 2H + + 2e- Ni(OH) 2 (s)...

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Chem 116 Lecture 22 (12/2/08) JL Oxidation Cu=0 N=+5 Cu=+2 N=+4 Number Element whose oxidation #s are changing. Cu: 0 to +2 oxidation. N: +5 to +4. reduction. Species on reactant side Species on the product side . Cu(s) is getting oxidized Cu 2+ (aq) NO 3 - is getting reduced. NO 2 (g) Oxidation half rxn: Cu Cu 2+ + 2e - We added 2 electrons to the product side to make the charge on the reactant side = charge on the product side. Reduction half-rxn: NO 3 - + 2H + NO 2 + H 2 O …water added N O 3 - + 2H + NO 2 + H 2 O …add - charge NO 3 - + 2H+ + 1e- NO 2 + H 2 O Oxid: Cu Cu 2+ + 2e - Red: (NO 3 - +2H + +1e - NO 2 + H 2 O) × 2 …× 2 to cancel e- out Cu + 2NO 3 - +4H + 2NO 2 + 2H 2 O + Cu 2+ Species on reactant side Cd(s) is getting oxidized => reducing agent NiO 2 (s) is getting reduced => oxidizing agent. Oxid.half-rxn. Cd(s) Cd(OH) 2 (s) Cd(s) + 2H 2 O Cd(OH) 2 (s) + 2H + Cd(s) + 2H 2 O Cd(OH) 2 (s) + 2H + + 2e - Reduction half-rxn: NiO 2 (s) Ni(OH) 2 (s) NiO 2 (s) + 2H + Ni(OH) 2 (s) NiO
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Unformatted text preview: 2 (s) + 2H + + 2e- Ni(OH) 2 (s) Cd(s) + 2H 2 O + NiO 2 (s) Cd(OH) 2 + Ni(OH) 2 In the Cu cell In the Zn cell Cu Cu 2+ Zn 2+ Zn Cu 2+ Cu Zn Zn 2+ (one of these two (one of these two things must be things must be happening) happening) use the reduction potentials to figure out which one of these cells is the oxidation (anode) and which is the reduction (cathode) Standard Reduction Potentials are: Cu 2+ + 2e- Cu E o = +0.332 v Zn 2+ + 2e- Zn E o = -0.763 v two possibilities. 1. Oxid. Cu Cu 2+ + 2e-E o = -0.337 v Red. Zn 2+ + e- Zn. E o = -0.763 v Cu + Zn 2+ Cu 2+ + Zn E o = -1.10 2. Oxid. Zn Zn 2+ + 2e-E o = +0.763 v Red. Cu 2+ + 2e- Cu E o = +0.337 v Zn + Cu 2+ Zn 2+ + Cu E o = +1.10 v possibility #2 is the reaction that occurs spontaneously since E o is +. possibility #1 possibility #2...
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This note was uploaded on 12/02/2011 for the course PHYSICS 235 taught by Professor Staff during the Fall '08 term at Rutgers.

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12-2-08[lecture22]jl - 2 (s) + 2H + + 2e- Ni(OH) 2 (s)...

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