`CoS` (black) obtained in group `IV` of salt analysis is dissolved in aqua regia and is treated with an excess of `NaHCO_(3)` and then `Br_(2)` water.An apple green coloured stable complex is formed. It is:

(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.

When 1 mole CrCl_(3).6H_(2)O is treated with excess of AgNO_(3), 3 mol AgCl are obtained. Formula of the complex :

When 1 mol CrCl_3 .6H_2O is treated with excess of AgNO_3 , 3 3 mol of AgCl are obtained. The formula of the complex is: