Practice Problem 9
Calculate the potential at 25oC for the following cell.
|Cu|||||Cu2+(0.024 M)||||||Ag+(0.0048 M)|||||Ag|
We start by translating the line notation into an equation for the reaction.
Cu(s) + 2 Ag+(aq) Cu2+(aq) + 2 Ag(s)
We then look up the standard-state potentials for the two half-reactions and calculate the standard-state cell potential.
|Oxidation:||Cu Cu2+ + 2 e-||Eoox = -(0.3402 V)|
|Reduction:||Ag+ + e- Ag||Eored = 0.7996 V|
|Eo = Eored + Eoox = 0.4594 V|
We now set up the Nernst equation for this cell, noting that n is 2 because two electrons are transferred in the balanced equation for the reaction.
Substituting the concentrations of the Cu2+ and Ag+ ions into this equation gives the value for the cell potential.