Question

When $KMn{O}_4$ acts as an oxidising agent and forms $Mn{O}_2$, the number of electrons transferred per molecule of $KMn{O}_4$ is :

Answer 1

Reaction when $KMn{O}_4$ acts as an oxidising agent and forms $Mn{O}_2$ is given below:
$\stackrel{+7}{Mn}{O}_4^{-}+3e^{-}\to \stackrel{+4}{Mn}{O}_2$
The oxidation state of $Mn$ in $Mn{O}_4^{-}$ and $Mn{O}_2$ are $+7$ and $+4$ respectively.
Therefore, change in oxidation state is $3$ which is the number of electrons transferred per molecule.