A certain inorganic compound (A) on heating loses water of crystallisation. On further heating a blackish brown powder (B) and two oxides of sulphur (C & D) are obtained. The powder (B) on boiling with HCl gives a yellow solution (E). When `H_(2)S` is passed in (E) a white turbidity (F) and an apple green solution (G) is obtained. The solution (E) on treatment with thiocyanate ion gives blood red compound (H). Identify (A) to (H).

Explanation

(A) on heating gives two oxides of S and thus it is `FeSO_(4).7H_(2)O`.
`1. underset((A))(FeSO_(4).7H_(2)O) overset(Delta)(rarr)FeSO_(4)+7H_(2)O`
2. `2FeSO_(4)overset(Delta)(rarr)underset((B))(Fe_(2)O_(3))+underset((C ))(SO_(2))+underset((D))(SO_(3))`
3. `Fe_(2)O_(3)+6HCl rarr 2FeCl_(3)+3H_(2)O`
4. `underset((E))(2FeCl_(3))+H_(2)S rarr underset((G))overset((E) "yellow")(FeCl_(2))+2HCl+underset("Turbidity (F)")(S)`
`Fe^(2+)overset(OH^(-)"oxidation")(rarr)Fe^(3+)`
`Fe^(3+)+3CNS^(-)rarr Fe(CNS)_(3)("blood Red colour")`