From sodium aurocyanide `Na[Au(CN)_2]` , gold can be precipitate adding powder of

Options

A. Hg
B. Ag
C. Zn
D. None of these

Answer

To solve the question of how to precipitate gold from sodium aurocyanide `Na[Au(CN)2]`, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Compound**: Sodium aurocyanide, `Na[Au(CN)2]`, is a complex compound where gold is in the form of a cyanide complex.

2. **Cyanide Process**: Gold can be extracted from ores using the cyanide process. This involves the dissolution of gold in a cyanide solution, forming a soluble complex.

3. **Precipitation Reaction**: To precipitate gold from its cyanide complex, a reducing agent is required. One common reducing agent used in this process is zinc powder.

4. **Chemical Reaction**: When zinc powder is added to the solution of sodium aurocyanide, it reacts with the gold cyanide complex to form zinc cyanide and precipitate gold. The reaction can be represented as:
\[ 2 \text{Na[Au(CN)}_2] + \text{Zn} \rightarrow 2 \text{Au} + \text{Na}_2\text{Zn(CN)}_4 \]
In this reaction, gold (Au) is precipitated out of the solution.

5. **Conclusion**: Therefore, the correct answer to the question is that gold can be precipitated by adding zinc powder.

### Final Answer:
Gold can be precipitated from sodium aurocyanide `Na[Au(CN)2]` by adding zinc powder.

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