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

Problem 18.52

Determine the values of Eocell and Go for the following reactions.

(a) Al(s) + 3 Ag+(aq)Al3+(aq) + 3 Ag(s)

(b) 4 IO3(aq) + 4 H+(aq) 2 I2(s) + 2 H2O(l) + 5 O2(g)




Answer:

(a) Al(s) + 3 Ag+(aq) Al3+(aq) + 3 Ag(s)

Al(s) Al3+(aq) + 3 e  Eooxidation = +1.676 V

Ag+(aq) + e Ag(s)  Eoreduction = +0.800 V

Eocell = Eooxidation + Eoreduction = 1.676 + 0.800 = 2.476 V

Go = –nFEocell = –(3)(96485)(2.476) = –716700 J = –716.7 kJ



(b) 4 IO3(aq) + 4 H+(aq) 2 I2(s) + 2 H2O(l) + 5 O2(g)

2 H2O(l) O2(g) + 4 H+(aq) + 4 e  Eooxidation = –1.229 V

2 IO3(aq) + 12 H+(aq) + 10 e I2(s) + 6 H2O(l)   Eoreduction = +1.20 V

Eocell = Eooxidation + Eoreduction = –1.229 + 1.20 = –0.03 V

Go = –nFEocell = –(20)(96485)(–0.03) = +60000 J = +60 kJ