A balck coloured compound (A) on reaction with dilute `H_(2)SO_(4)` gives a gas (B) which on passing in a solution of an acid (C ) gives a white turbidity (D). Gas (B ) when passed in an acidified solution of a compound (E ) gives a precipitate (F) soluble in dil `HNO_(4)` . After boiling this solution when an excess of `NH_(4)OH` is added, a blue coloured compound (G) is formed. To this solution on addition of acetic acid and aqueous `K_(4)[Fe(CN)_(6)]` a chocolate precipitate (H) is obtained. On addition of an aqueous solution of `BaCl_(2)` to an aqueous solution of `(E)`, a white precipitate insolution in `HNO_(3)` is obtained. Identify (A) to (H).

Explanation

(1) The black coloured compound may be FeS, CuS or PbS, CoS, NiS but FeS reacts with dil. `H_(2)SO_(4)` to produce `H_(2)S`
`underset((A))(MS)+H_(2)SO_(4)rarr MSO_(4)+underset((B))(H_(2)S)`
(2) Gas `H_(2)S` on passing through `HNO_(3)` gives turbidity of S.
`underset((B))(H_(2)S )+underset((C ))(2HNO_(3))rarr2NO_(2)+2H_(2)O+underset((D))(S)`
(3)(E) is `CuSO_(4)` because it gives white precipitate of `BaSO_(4)` with `BaCl_(2) &` blue color with `NH_(4)OH`.
`underset((E))(CuSO_(4))+BaCl_(2)rarr CuCl_(2)+underset("white")(BaSO_(4))`
(4) Gas (B) i.e. `H_(2)S` gives black precipitate with `CuSO_(4)`
`underset((E))(CuSO_(4))+H_(2)S rarr underset((F)"black")(CuS)+H_(2)SO_(4)`
(5) Compound F(CuS) gives `Cu(NO_(3))_(2)` with `HNO_(3)` which on treating with `NH_(4)OH` gives blue colour.
`underset((F))(CuS)+2HNO_(3)rarrCu(NO_(3))_(2)+H_(2)S`
`Cu(NO_(3))_(2)+4NH_(4)OHrarr [Cu(NH_(3))_(4)](NO_(3))_(2)+4H_(2)O`
(G) blue
(6) (G) on acidifying with `CH_(3)COOH` and then treating with `K_(4) Fe9CN)_(6)` gives chocolate coloured precipitate of `Cu_(2)Fe(CN)_(6)`.
`Cu(NH_(3))_(4).(NO_(3))_(2)+4CH(3)COOH rarr Cu9NO_(3))_(2)+4CH_(3)COONH_(4)`
`2Cu(NO_(3))_(2)+K_(4)Fe(CN)_(6)rarrCu_(2)[Fe(CN)_(6)+4KNO_(3)`.
`[A] : FeS`