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

Problem 18.58

What is the value of Ecell of each of the following reactions when carried out in a voltaic cell?

(a) Fe(s) + 2 Ag+(aq, 0.0015 M)Fe2+(aq, 1.33 M) + 2 Ag(s)

(b) 4 VO2+(aq, 0.050 M) + O2(g, 0.25 atm) + 2 H2O(l)4 VO2+(aq, 0.75 M) + 4 H+(aq, 0.30 M)




Answer:

Assume 25 oC = 298 K

(a) Fe(s) + 2 Ag+(aq, 0.0015 M)Fe2+(aq, 1.33 M) + 2 Ag(s)

Fe(s)Fe2+(aq) + 2 e    Eoox = +0.440 V

Ag+(aq) + eAg(s)    Eored = +0.800 V

Eocell = Eoox + Eored = 0.440 + 0.800 = 1.240 V

Ecell = +1.069 V



(b) 4 VO2+(aq, 0.050 M) + O2(g, 0.25 atm) + 2 H2O(l)4 VO2+(aq, 0.75 M) + 4 H+(aq, 0.30 M)

VO2+(aq) + H2O(l)VO2+(aq) + 2 H+(aq) + e    Eoox = –1.000 V

O2(g) + 4 H+(aq) + 4 e2 H2O(l)    Eored = +1.229 V

Eocell = Eoox + Eored = –1.000 + 1.229 = 0.229 V

Ecell = +0.181 V