`Ag_(2)S +NaCN rarr (a)`
(a) `+Zn rarr (d)`
(b) is a metal. Hence `(a)` and `(b)` are

Options

A. `Na_(2)[Zn(CN)_(4)],Zn`
B. `Na[Ag(CN)_(2)],Ag`
C. `Na_(2)[Ag(CN)_(4),Ag`
D. `Na_(3)[Ag(CN)_(4)],Ag`

Explanation

To solve the given question step by step, we will analyze the reactions involving silver sulfide (Ag₂S) and sodium cyanide (NaCN), followed by the reaction with zinc (Zn).

### Step 1: Identify the reaction of Ag₂S with NaCN
When silver sulfide (Ag₂S) reacts with sodium cyanide (NaCN), it forms a complex compound known as sodium di-cyano-argentate. The reaction can be represented as follows:

\[ \text{Ag}_2\text{S} + 4 \text{NaCN} \rightarrow 2 \text{Na}_2\text{[Ag(CN)}_2\text{]} + \text{Na}_2\text{S} \]

In this reaction, sodium sulfide (Na₂S) is also produced alongside the complex.

### Step 2: Identify the complex formed
The complex formed in the reaction is sodium di-cyano-argentate, which can be represented as:

\[ \text{Na}_2\text{[Ag(CN)}_2\text{]} \]

This complex is denoted as (a) in the question.

### Step 3: Reaction of the complex with zinc (Zn)
Next, the sodium di-cyano-argentate complex reacts with zinc. Zinc is a more reactive metal than silver and can displace silver from the complex. The reaction can be represented as follows:

\[ \text{Na}_2\text{[Ag(CN)}_2\text{]} + \text{Zn} \rightarrow \text{Na}_2\text{[Zn(CN)}_4\text{]} + 2 \text{Ag} \]

In this reaction, sodium tetra-cyano-zincate is formed along with the precipitation of silver metal.

### Step 4: Identify the products (a) and (b)
From the reactions:
- (a) is sodium di-cyano-argentate \(\text{Na}_2\text{[Ag(CN)}_2\text{]}\)
- (b) is zinc (Zn), which is the metal used in the reaction.

### Final Answer
Thus, (a) is sodium di-cyano-argentate, and (b) is zinc.

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