Extraction of gold and silver involves leaching the metal with `CN^(-)` ion. The metal is recovered by :

Options

A. displacemetn of metal by some other metal from the complex ion
B. roasting of metal complex
C. calcination followed by roasting
D. thermal decomposition of metal complex.

Answer

To solve the question regarding the extraction of gold and silver through leaching with cyanide ions, we will break down the process step by step.

### Step-by-Step Solution:

1. **Leaching Process**:
- Gold (Au) and Silver (Ag) are extracted from their ores by leaching with cyanide ions (CN⁻).
- This process forms a water-soluble complex, specifically [Au(CN)₂]⁻ for gold and [Ag(CN)₂]⁻ for silver.

2. **Formation of Complex**:
- The reaction can be represented as:
- For Gold:
\[ \text{Au} + 2 \text{CN}^- \rightarrow [\text{Au(CN)}_2]^- \]
- For Silver:
\[ \text{Ag} + 2 \text{CN}^- \rightarrow [\text{Ag(CN)}_2]^- \]

3. **Recovery of Metals**:
- The next step involves recovering the metals from their respective complexes. This is achieved by using a reducing agent.
- Zinc (Zn) is commonly used as it is a cheap and effective reducing agent.

4. **Reduction Reaction**:
- The reduction of the metal complex can be represented as:
- For Gold:
\[ [\text{Au(CN)}_2]^- + \text{Zn} \rightarrow \text{Au} + [\text{Zn(CN)}_4]^{2-} \]
- For Silver:
\[ [\text{Ag(CN)}_2]^- + \text{Zn} \rightarrow \text{Ag} + [\text{Zn(CN)}_4]^{2-} \]

5. **Conclusion**:
- The recovery of gold and silver from their cyanide complexes is achieved through the displacement of the metal by zinc, which acts as a reducing agent.

### Final Answer:
The metal is recovered by **displacement of metal by some other metal from the complex ion** (Option A).

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