Lecture16, 2-15-08 Batteries

# Lecture16, 2-15-08 Batteries - Calculation of E,...

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Calculation of E, Non-standard Cell Zn(s)|Zn 2+ (1.00M) Cu 2+ (0.05M)|Cu(s) Write the balanced cell reaction Zn(s) + Cu 2+ (0.05M) Zn 2+ (1.00M) + Cu(s) Is E > or < E o ? Concentrations indicate E less than E o Look for concentration effect

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Calculation of E, Non-standard Cell Q log n 0592 . 0 E E ° = [ ] [] ( ) () 20 05 . 00 . 1 2 2 = = = + + Cu Zn Q Zn(s) + Cu 2+ (0.05M) Zn 2+ (1.00M) + Cu(s) ( ) ( ) V 103 . 1 cell E ) V 763 . 0 ( V 340 . 0 Zn / Zn E Cu / Cu E cell E o 2 2 / 1 o 2 2 / 1 o o = = = + + Evaluate E V V V E V E 065 . 1 038 . 0 103 . 1 20 log 2 0592 . 0 103 . 1 = = = Nernst Equation Evaluate Q Evaluate E o Note n=2
Free Energy and Cell Potential Zn(s) + Cu 2+ (0.05M) Zn 2+ (1.00M) + Cu(s) () ( ) ( ) ) 206 (~ 545 , 205 / 065 . 1 / 500 , 96 2 kJ J G coulomb joule mole coulomb mole G nFE G = Δ = Δ = Δ 2 Zn(s) + 2 Cu 2+ (0.05M) 2 Zn 2+ (1.00M) + 2 Cu(s) Q log n 0592 . 0 E E ° = [ ] [] 20 log 2 059 . 20 log 2 4 059 . 20 log 059 . 20 05 . 00 . 1 2 2 2 2 2 2 2 2 = = = = = + + n Cu Zn Q E is unchanged,1.065V G = -4 FE G = -412 kJ

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Effect of Concentration on Cell EMF Effect of Concentration on Cell EMF Cell EMF and Chemical Equilibrium Cell EMF and Chemical Equilibrium • A system is at equilibrium when Δ G = 0. • From the Nernst equation, at equilibrium: . 0592 . 0 log . log 0592 . 0 0
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## This note was uploaded on 08/06/2008 for the course CHEM 1B taught by Professor Watts during the Winter '08 term at UCSB.

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Lecture16, 2-15-08 Batteries - Calculation of E,...

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