(i)An inorganic compound (A) is formed on passing a gas (B) through a concentrated liquor containing sodium sulphide and sodium sulphite.
(ii) On adding (A) into a dilute solution of silver nitrate, a white precipitate appears which quickly changes into a black coloured compound (C).
(iii) On adding two or three drops of ferric chloride into an excess of solution of (A), a violet coloured compound (D) is formed. But this colour disappears quickly.
(iv) On adding a solution of (A) into the solution of cupric chloride, a white precipitate is first formed which dissolves on adding excess of (A) forming a compound (E). Identify (A) to (E) and give chemical equations for the reactions at steps (i) to (iv).

Explanation

To solve the problem step by step, we will identify the compounds (A) to (E) and provide the corresponding chemical equations for each reaction described in the question.

### Step 1: Identifying Compound A and Gas B
The question states that an inorganic compound (A) is formed by passing a gas (B) through a concentrated solution containing sodium sulfide (Na2S) and sodium sulfite (Na2SO3).

- The gas (B) is sulfur dioxide (SO2).
- The reaction can be represented as follows:

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