Question

Acidified $KMn{O}_4$ is decolourized by:

• A. ferric ammonium alum
• B. mohr's salt
• C. haematite
• D. a neutral ferric chloride solution

Answer 1

Answer: (B)

mohr's salt

Acidified $KMn{O}_4$ is decolourised by Mohr's salt ($\left(N{H}_4{)}_{2}Fe\right(S{O}_4{)}_2.6H_{2}O$). The chemical equation for the reaction taking place can be written as:
$Mn{O}_4^{-}+F{e}^{2+}\stackrel{H^{+}}{\to }M{n}^{2+}+F{e}^{3+}$