Question

Acidified potassium permanganate is decolourised by:

• A. White vitriol
• B. Bleaching powder
• C. laughing gas
• D. Mohr's salt

Answer 1

The correct option is D Mohr's salt

Acidified potassium permanganate is decolourised by Mohr's salt.

In this reaction, Mohr salt acts as a reducing agent and potassium permanganate as an oxidising agent. In this redox reaction, ferrous ion from Mohr's salt gets oxidised and pink coloured of manganese which presents in potassium permanganate in +7 oxidation state gets reduced to +2 state and become colourless.

Overall reaction:

$Mn{O}_4^{-}+8H^{+}+5F{e}^{2+}\to M{n}^{2+}+5F{e}^{3+}+4H_{2}O$