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 solution to give purple compound (C). An alkaline solution of compound (C) oxidizes potassium iodide solution to a compound (D) and compound (A) is also formed. Identify compounds A to D and also explain the reactions involved.
A=MnO2, B=K2MnO4, C= KMnO4, D= KIO3
When Manganese dioxide(A) is fused with KOH, it gives a green solution of potassium manganate(B).
2MnO2 (A) + 4KOH +O2→ 2K2MnO4(B) +2H2O
Potassium manganate disproportionates to give purple potassium permanganate(C).
3MnO42- +H+→2MnO4-(C)+MnO2 +2H2O
Potassium permanganate on reacting with KI gives potassium iodate(D) and manganese dioxide again
2MnO4- +H2O +KI → 2MnO2 + 2OH- + KIO3(D)