When an oxide of manganese (A) is fused with KOH in the presence of an oxidising agent and dissolved in water, it gives a dark green solution of compound (B). Compound (B) disproportionates in neutral or acidic (C ) oxidises potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.

Explanation

It is the method of preparation of potassium permanganate (purple).
Thus, (A) = `MnO_(2) " "(B) = K_(2)MnO_(4)`
(C ) = `KMnO_(4) " "(D) = KIO_(3)`
`2Mn underset([A])(O_(2)) + 4KOH + O_(2) rarr 2K_(2)underset([B])(MnO_(4)) + 2H_(2)O`
`3MnO_(4)^(2-) + 4H^(+)rarrunderset([B])(2MnO_(4)^(-))+MnO_(2)+2H_(2)O`
`2MnO_(4)^(-) + H_(2)O + KI rarr 2underset([A])(MnO_(2)) + 2OH^(-) + underset([D]) (KIO_(3))`