(i)A black coloured compound `(B)` is formed on passing `H_(2)S` through the solution of a compound `(A)` in `NH_(4)OH`
(ii)`(B)` on treatment with `HCl` and potassium chlorate or aquaregia gives `(A)`
(iii)`(A)` on treatment with `KCN` gives a buff/reddish-brown coloured precipitate which dissolves in excess of this reagent forming a compound `( C)`.
(iv)The compound `( C)` is changed into a compound `(D)` when its aqueous solution is boiled in air.
(v)The solution of `(A)` was treated with excess of `NaHCO_(3)` & then with bromine water. On cooling & shaking for some time, a green colour of compound `(E)` is formed.No change is observed on heating.
Identify `(A)` to `(E)` and give chemical equations.

Explanation

The formation of black coloured compound (B) by passing `H_(2)S` through the alkaline solution of the compound indicate that this asalt of the group TV TMCats (`Co^(2+)` or `Ni^(2+)`). However, the given reactions especially, reaction (ili), indicates that compound (A) is a cobalt salt `(CoCl_(2))` which explains all the given reactions.
(i) `underset((A))(CoCl_(2))+2NH_(4)OH+H_(2)Stounderset((B))(CoS)+2NH_(4)Cl+2H_(2)O`
(ii) `CoS+2HCl+underset((from KClO_(3)))([O])toCoCl_(2)+H_(2)S`
`2KlCO_(3)to2Kcl+3O_(2)`
(iii) `CoCl_(2)+2KCNtoCo(CN)_(2)darr+2Kcl`
`Co(CN)_(2)+4KCNtoK_(4)[Co(CN)_(6)]`
(iv) `2K_(4)[Co(CN)_(6)]+[O]+H_(2)Oto2K_(3)[Co(CN)_(6)]+2KOH`
(v) `CoCl_(2)+6NaHCO_(3)toNa_(4)[Co(CO_(3))_(3)]+2NaCl+3CO_(2)+3H_(2)O`
`2Na_(4)[Co(CO_(3))_(3)]+2NaHCO_(3)+Oto2Na_(3)[Co(CO_(3))_(3)]+2Na_(2)CO_(3)+H_(2)O`