Question

How is the oxidation of `"ferrous ion"` to `"ferric ion"` by `"permanganate ion"` represented?

Answer 1

We write out the individual redox processes to get:

`MnO_4^(-) + 5Fe^(2+) +8H^(+)rarr Mn^(2+) + 5Fe^(3+) +4H_2O(l)`

Explanation:

`"Oxidation reaction (i):"`

`Fe^(2+) rarr Fe^(3+) + e^-`

`"Reduction reaction (ii):"`

`MnO_4^(-) + 8H^(+) + 5e^(-) rarr Mn^(2+) + 4H_2O(l)`

For both `(i)` and `(ii)`, `"charge is balanced"` and `"mass is balanced"`, as indeed they must be if we purport to represent chemical reality. The final redox reaction adds `5xx(i)+(ii)` so that electrons, conceptual particles, do not appear in the final redox equation:

`MnO_4^(-) + 5Fe^(2+) +8H^(+)rarr Mn^(2+) + 5Fe^(3+) +4H_2O(l)`

Which is balanced (is it?) with respect to mass and charge. The reaction has a built in indicator in that `MnO_4^-` in intensely purple, whereas the reduction product `Mn^(2+)` is almost colourless. An endpoint could be vizualized.