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J. W. Hill, R. H. Petrucci, T. W. McCreary, & S. S. Perry General Chemistry 4th edition

Problem 18.36

For the reaction

2 CuI(s) + Cd(s)Cd2+(aq) + 2 I(aq) + 2 Cu(s)   Eocell = +0.23 V

given that EoCd2+/Cd = –0.403 V, determine Eo for the half–reaction

2 CuI(s) + 2 e2 Cu(s) + 2 I(aq)




Answer:

The two half–reaction for the cell are:

2 CuI(s) + 2 e2 Cu(s) + 2 I(aq)   Eoreduction = ?

Cd(s) Cd2+(aq) + 2 e  Eooxidation = –Eoreduction = –(–0.403) = +0.403 V

For the net cell, Eocell = Eoreduction + Eooxidation = +0.23 V

Substituting,

+0.23 = Eoreduction + 0.403

Eoreduction = –0.17 V