Question

A salt contains cation $A^{2+}$ and anion $B^{2-}$. Both decolourise ${MnO}_4^{-}$ is acidic medium. Salt is :

• A. ferrous oxalate
• B. ferric oxalate
• C. both (a) and (b)
• D. None of these

Answer 1

The correct option is A ferrous oxalate

The salt is ferrous oxalate. In acidic medium, potassium permanganate acts as a strong oxidizing agent.
It oxidizes both ferrous ion and oxalate ion.
Ferrous ion is oxidized to ferric ion and oxalate ion is oxidized to carbon dioxide.
Hence, the cation and the anion in the salt ferrous oxalate decolourizes permanganate ion in acidic medium.
$2Mn{O}_4^{-}+5C_2{O}_4^{2-}+16H^{+}\to 2M{n}^{2+}+10C{O}_2+8H_{2}O$
$Mn{O}_4^{-}+5F{e}^{2+}+8H^{+}\to 5F{e}^{3+}+M{n}^{2+}+4H_{2}O$