Ncert Exercises & Solutions

${MnO}_{4}^{2 -}$ undergoes disproportionation reaction in acidic medium but ${MnO}_{4}^{-}$ does not. Give reason.

In

{MnO}_{4}^{2 -}

, the oxidation number of Mn is +6. It can increase its oxidation number (to +7) or decreases its oxidation number (to +4, +3, +2, 0).

Hence, it undergoes disproportionation reaction in acidic medium.

In

{MnO}_{4}^{2 -}

, Mn is in its highest oxidation state, i.e., +7. It can only decrease its oxidation number. Hence, it cannot undergo disproportionation reaction.