Question

Why is the `E^(ɵ)` value for the `Mn^(3+)//Mn^(2+)` couple much more position than that for `Cr^(3+)//Cr^(2+)" or "Fe^(3+)//Fe^(2+)` ? Explain.

Answer 1

Much larger third ionisation energy of Mn (where the required change is `d^(5)" to "d^(4))` is mainly responsible for this. This also explains why the +3 state of Mn is of little importance.