Question

Explain why does colour of $KMn{O}_4$ disappear when oxalic acid is added to its solution in acidic medium.

Answer 1

Potassium permanganate $KMn{O}_4$is an oxidizing agent which exists as a purple colour solution.

In acidic medium, when $KMn{O}_4$ is added to oxalic acid, it oxidizes oxalic acid to $C{O}_2$ and itself gets reduced to $M{n}^{2+}$

The colour of $KMn{O}_4$ disappears due to the formation of $M{n}^{2+}$ ions which are colourless. The reaction is as follows:

$2MnO{{}_4}^{-}+5C_{2}O{{}_4}^{2-}+16H^{+}\to 2M{n}^{2+}+8H_{2}O+10C{O}_2$

$MnO{{}_4}^{-}$: coloured

$M{n}^{2+}$: colourless