In the leaching of `Ag_(2)S` with `NaCN`, a stream air is also passed. It is because of

Options

A. reversible nature of eaction between `Ag_(2)S` and NaCN
B. to oxide `Na_(2)S` formed into `Na_(2)SO_(4)` and sulphur
C. both (a) and (b)
D. none of the above

Answer

To solve the question regarding the leaching of \( \text{Ag}_2\text{S} \) with \( \text{NaCN} \) and the reason for passing a stream of air, we can break down the process step by step.

### Step-by-Step Solution:

1. **Understanding Leaching**:
Leaching is a process in extractive metallurgy where valuable metals are converted into soluble salts using chemicals, allowing impurities to remain insoluble and be washed away. In this case, we are focusing on the leaching of silver from silver sulfide (\( \text{Ag}_2\text{S} \)).

**Hint**: Leaching is a method used to extract metals from ores by dissolving them in a solvent.

2. **Chemical Reaction Involved**:
The leaching of \( \text{Ag}_2\text{S} \) with \( \text{NaCN} \) can be represented by the following reaction:
\[ \text{Ag}_2\text{S} + 4 \text{NaCN} \rightarrow 2 \text{NaAgCN} + \text{Na}_2\text{S} \]
This reaction produces a soluble complex \( \text{NaAgCN} \) and sodium sulfide (\( \text{Na}_2\text{S} \)).

**Hint**: Identify the products formed from the reaction of silver sulfide with sodium cyanide.

3. **Role of Air**:
A stream of air is passed during the leaching process to oxidize the sodium sulfide (\( \text{Na}_2\text{S} \)) that is formed. The oxidation reaction can be represented as:
\[ 4 \text{Na}_2\text{S} + 5 \text{O}_2 + 2 \text{H}_2\text{O} \rightarrow 4 \text{Na}_2\text{SO}_4 + 2 \text{S} \]
This reaction converts sodium sulfide into sodium sulfate (\( \text{Na}_2\text{SO}_4 \)) and sulfur (\( \text{S} \)).

**Hint**: Consider why oxidation is necessary in the process and what products are formed.

4. **Reversible Nature of the Reaction**:
The reaction between \( \text{Ag}_2\text{S} \) and \( \text{NaCN} \) is reversible. This means that the products can react back to form the reactants under certain conditions. The presence of air helps drive the reaction towards the formation of soluble complexes and prevents the backward reaction.

**Hint**: Reflect on the significance of reversible reactions in chemical processes.

5. **Conclusion**:
Therefore, the reason for passing a stream of air during the leaching of \( \text{Ag}_2\text{S} \) with \( \text{NaCN} \) is twofold:
- To oxidize \( \text{Na}_2\text{S} \) formed into \( \text{Na}_2\text{SO}_4 \) and sulfur.
- The reaction is reversible, and passing air helps to shift the equilibrium towards the products.

**Final Answer**: The correct answer is **C**: both A and B are correct.