E°Fe2+∕Fe=−0.44V E°Fe3+∕Fe2+=−0.77V If a cell is constructed combining these two electrodes oxidation occurs at Fe2+∕Fe electrode. At anode :Fe→Fe2++2e− At cathode :[Fe3++e−→Fe2+]×2 Cell reaction : Fe+2Fe3+→3Fe2+ If Fe2+,Fe3+ and Fe block are kept together then Fe3+ reacts with Fe to yield Fe2+ i.e. concentration of Fe3+ is decreased.