The overall cell reaction is given as: Fe+2Fe3+→3Fe2+.
This reaction can be split into two half-reactions:
- Oxidation at Anode: Fe→Fe2++2e− (Standard reduction potential, Eanode∘=EFe2+/Fe∘=−0.441 V)
- Reduction at Cathode: 2Fe3++2e−→2Fe2+ (Standard reduction potential, Ecathode∘=EFe3+/Fe2+∘=0.771 V)
The standard emf of the cell (Ecell∘) is calculated using the formula:
Ecell∘=Ecathode∘−Eanode∘
Ecell∘=0.771 V−(−0.441 V)
Ecell∘=0.771 V+0.441 V=1.212 V
Note: Standard electrode potential is an intensive property . Therefore, multiplying the stoichiometric coefficients of the reduction half-reaction by 2 to balance the electrons does not change the value of its E∘.