Chapt. 18 Electrochemistry Sec. 5  G° from E° © University of South Carolina Board of Trustees

 G and Cell Potential work available from reaction electrical work done by cell =  G and E ° both predict spontaneity

© University of South Carolina Board of Trustees  G and Cell Potential  G ° cell = - n F E ° cell work available from reaction electrical work done by cell =  G and E ° both predict spontaneity E° cell =  E o 1/2

© University of South Carolina Board of Trustees  G° from Standard Potentials Calculate  G ° cell for the reaction AgCl (s)  Ag + (aq) + Cl - (aq) AgCl (s) + e -  Ag (s) + Cl - (aq) E ° 1/2 = V Ag + (aq) + e -  Ag (s) E ° 1/2 = V

© University of South Carolina Board of Trustees Student Example Calculate  G ° cell for the reaction 2Na (s) + 2H 2 O (ℓ)  2Na + (aq) +2OH - (aq) +H 2 (g) 2Na + (aq) + 2e -  2Na (s) E ° 1/2 = V 2H 2 O (ℓ) + 2e -  H 2(g) + 2OH - (aq) E ° 1/2 = V

Chapt. 18 Electrochemistry Sec. 5 K eq from E° © University of South Carolina Board of Trustees

K eq and Cell Potential K eq   G °  E ° cell E° cell

© University of South Carolina Board of Trustees K eq from E º Determine K eq for the reaction at 25°C Fe (s) + Pb 2+ (aq)  Pb (s) + Fe 2+ (aq) if the concentrations are 1.0 M (standard conditions) Fe 2+ (aq) + 2e -  Fe (s) E ° 1/2 = V Pb 2+ (aq) + 2e -  Pb (s) E ° 1/2 = V

© University of South Carolina Board of Trustees Student Example Determine K eq for the reaction at 25°C 2Ag (s) + Ni 2+ (aq)  Ni (s) + 2Ag + (aq) if the concentrations are 1.0 M (standard conditions) Ni 2+ (aq) + 2e −  Ni (s) E ° 1/2 = −0.25 V Ag + (aq) + e −  Ag (s) E ° 1/2 = V

© University of South Carolina Board of Trustees Chapt. 18 Electrochemistry Sec. 6 Non-Standard Concentrations

© University of South Carolina Board of Trustees non-Standard Concentrations cell Nernst Equation Allows for the prediction of voltages under non-standard conditions

© University of South Carolina Board of Trustees Example: Nernst Equation What is the cell potential for a cell made up of Zn, M Zn(NO 3 ) 2, Cu, and M Cu(NO 3 ) 2 ? Zn 2+ (aq) + 2e −  Zn (s) E ° 1/2 = −0.76 V Cu 2+ (aq) + 2e −  Cu (s) E ° 1/2 = V

© University of South Carolina Board of Trustees Student Example: Nernst Equation What is the cell potential for a cell made up of Cu, M Cu(NO 3 ) 2, Fe, and M FeSO 4 ? Fe 2+ (aq) + 2e −  Fe (s) E ° 1/2 = −0.44 V Cu 2+ (aq) + 2e −  Cu (s) E ° 1/2 = V