# How do "MnO"_2 and "KMnO"_4 behave? Oxidizing or reducing agents?

Dec 14, 2016

$\text{Manganese (IV) oxide}$ and $K M n {O}_{4}$ are $\text{oxidizing agents.}$

#### Explanation:

$M {n}^{2 +}$ is the reduction product. Because this is a ${d}^{5}$ high spin metal centre, its electronic transitions are spin-forbidden, and a solution of $M {n}^{2 +}$ is (almost!) completely colourless (very conc. solutions are a pale rose).

So, when we take strongly oxidizing permanganate ion, which is very strongly coloured, the redox reaction has a self-indicating end-point, and decolorizes:

$M n {O}_{4}^{-} + 8 {H}^{+} + 5 {e}^{-} \rightarrow M {n}^{2 +} + 4 {H}_{2} O$

We habitually use this reaction in redox titrations.