Question

Fusion of $MnO_2$ with $KOH$ in presence of $O_2$ produces a salt $W$. Alkaline solution of $W$ upon electrolytic oxidation yields another salt $X$. The manganese containing ions present in $W$ and $X$, respectively, are $Y$ and $Z$. Correct statement(s) is(are)

• A. In aqueous acidic solution, $Y$ undergoes disproportionation reaction to give $Z$ and $MnO_2$
• B. Both $Y$ and $Z$ are coloured and have tetrahedral shape
• C. $Y$ is diamagnetic in nature while $Z$ is paramagnetic
• D. In both $Y$ and $Z$, $\pi$-bonding occurs between $p$-orbitals of oxygen and $d$-orbitals of manganese

Answer 1

Answer: (A), (B), (D)

$\underset{\text{}}{2MnO_2} + 4KOH + O_2 \xrightarrow{\text{Fusion}} \underset{\text{(W)}}{2K_2MnO_4 + 2H_2O }$
Electrolysis of aq $K_2MnO_4$ oxidises $MnO^{2-}_{4}$ to $MnO^{-}_{4}$
$\underset{\text{(W)}}{K_2MnO_4} + 2H_2O \xrightarrow{\text{Electrolysis}} \underset{\text{(X)}}{2K_2MnO_4 + 2KOH + H_2 }$
$K_2MnO_4$ in acidic medium undergoes disproportionation
$\underset{\text{(Y)}}{3MnO^{2-}_{4}} + 4H^+ \rightarrow \underset{\text{(Z)}}{2MnO^{-}_{4} + MnO_2 + 2H_2O }$
$K_2MnO_4$ is green in colour and $KMnO_4$ is in purple colour. Both are tetrahedral in shape involving p$\pi$ - d$\pi$ bond.