(a) A blackish brown coloured solid 'A' when fused with alkali metal hydroxide in presence of air, produces a dark green coloured compoun 'B', which on electrolytic oxidation in alkaline mediumgives a dark purplecoloured compound C. Identify A,B and C and write the reaction involved. (b) Whathappens when an acidic solution of the green compound (B) is allowed to stand for some time ? Give the equation involved. What is this type of reaction called ?

(a) A blackish brown coloured solid 'A' when fused with alkali metal h

1.	(a) A blackish brown coloured solid 'A' when fused with alkali metal hydroxide in presence of air, produces a dark green coloured compoun 'B', which on electrolytic oxidation in alkaline mediumgives a dark purplecoloured compound C. Identify A,B and C and write the reaction involved. (b) Whathappens when an acidic solution of the green compound (B) is allowed to stand for some time ? Give the equation involved. What is this type of reaction called ?
Answer» Solution :(a) `underset("(A)BLACKISH brown")underset("Pyrolusite")(MnO_(2)) + 4KOH + O_(2) overset("Fuse")(rarr) underset("(B) - Green coloured")underset("Potassium manganate ")( 2K_(2)MnO_(4))+ 2H_(2)O` `underset((B))(2K_(2)MnO_(4)) + H_(2)O+(O) underset("medium")overset("Alkaline")(rarr) underset("(C ) -Purple coloured")underset("Potassium permanganate")(2KMnO_(4)) + 2KOH` or `MnO_(4)^(2-) rarrMnO_(4)^(-) + E^(-)` (b) When acidic solution of green compound (B) , i.e., potassium manganate is allowed to stand for some time, it disproportionates to GIVE permanganate as follows `:` `3MnO_(4)^(2-) + 4H^(+) rarr 2MnO_(4)^(-) + MnO_(2) + 2H_(2)O` This reaction is called disproportionation reaction.