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

The Correct Option is D

${ $\underset{\text{}}{{2MnO2}}$ + 4KOH + O2 ->[Fusion] $\underset{\text{(W)}}{{2K2MnO4 + 2H2O}}$ }$
Electrolysis of aq $K_2MnO_4$ oxidises $MnO^{2-}_{4}$ to $MnO^{-}_{4}$
${ $\underset{\text{(W)}}{{K2MnO4}}$ + 2H2O ->[Electrolysis] $\underset{\text{(X)}}{{2K2MnO4 + 2KOH + H2}}$ }$
$K_2MnO_4$ in acidic medium undergoes disproportionation
${ $\underset{\text{(Y)}}{{3MnO^{2-}_{4}}}$ + 4H+ -> $\underset{\text{(Z)}}{{2MnO^{-}_{4} + MnO2 + 2H2O}}$ }$
$K_2MnO_4$ is green in colour and $KMnO_4$ is in purple colour. Both are tetrahedral in shape involving p$\pi$ - d$\pi$ bond.