It is found that sometimes a relatively less stable oxidation state undergoes an oxidation−reduction reaction in which it is simultaneously oxidised and reduced. This is called disproportionation.
For example,
(a)
![\[CrO_4^{3 - } + 8{H^ + } \to 2CrO_4^{2 - } + C{r^{3 + }} + 4{H_2}O\]](https://www.learnatnoon.com/s/wp-content/ql-cache/quicklatex.com-31743c4303f8efda3052a50360fbc1b7_l3.png "Rendered by QuickLaTeX.com")
Cr(V) is oxidized to Cr(VI) and reduced to Cr(III).
(b)
![\[3MnO_4^{2 - } + 4{H^ + } \to 2MnO_4^ - + Mn{O_2} + 2{H_2}O\]](https://www.learnatnoon.com/s/wp-content/ql-cache/quicklatex.com-302d3d4ad11d99625acebd1e08a3eae9_l3.png "Rendered by QuickLaTeX.com")
Mn (VI) is oxidized to Mn (VII) and reduced to Mn (IV).