Identify A to E. Pyrolusite on heating with KOH in the presence of air gives a dark green compound (A). The solution of (A) on treatment with `H_2SO_4` gives a purple coloured compound `(B)`, which gives the following reactions:
(a). KI on reaction with alkaline solution of (B) changes into a compound (C).
(b). The colour of the compoud (B) disappears on treatment with the acidic solution of `FeSO_4`.
(c). With conc. `H_2SO_4` compound (B) gives (D) which can compose to yield (E) and oxygen.

Explanation

`2MnO_2+4KOH+underset((Air))(O_2)tounderset((A)Dark green)(2K_2MnO_4)+2H_2O`
`3K_2MnO_4+2H_2SO_4tounderset((B)purpl e)(2KMnO_4)+MnO_2+2K_2SO_4+2H_2O`
(a). `2KMnO_4+H_2O+KItoKIO_3(C)+2MnO_2+2KOH`
(b). `2KMnO_4+8H_2SO_4+10FeSO_4toK_2SO_42MnSO_4+5Fe_2(SO_4)_3+8H_2O`
(d). `2KMnO_4+H_2SO_4toMn_2O_7(D)+K_2SO_4+H_2O`
`2MnO_2O_7to4MnO_2(E)+3O_2`