During the test of halogens by silver nitrate test, the sodium extract is first boiled with a few drops of conc. `HNO_3` to

Options

A. decompose sodium halides present
B. decompose sodium cyanide if present
C. decompose sodium sulphide if present
D. acidify the sodium extract.

Explanation

### Step-by-Step Solution:

1. **Understanding the Sodium Extract**: The sodium extract is a solution that contains sodium salts of various anions, including halides, cyanides, and sulfides. This solution is prepared by boiling the organic compound with sodium hydroxide.

2. **Boiling with Concentrated Nitric Acid**: When the sodium extract is boiled with a few drops of concentrated nitric acid (HNO₃), it serves multiple purposes. The nitric acid is a strong oxidizing agent and can react with certain anions present in the sodium extract.

3. **Decomposition of Sodium Compounds**:
- **Sodium Cyanide (NaCN)**: When NaCN reacts with HNO₃, it decomposes to form sodium nitrate (NaNO₃) and releases nitrogen oxides (NO or NO₂) as gases.
- **Sodium Sulfide (Na₂S)**: Similarly, sodium sulfide can decompose in the presence of nitric acid to form sodium nitrate and sulfur compounds.
- **Halides**: Although the primary goal is to test for halides, the nitric acid does not directly decompose sodium halides but rather helps in the precipitation of silver halides when silver nitrate (AgNO₃) is added later.

4. **Acidification of the Sodium Extract**: The addition of concentrated nitric acid also acidifies the sodium extract. This is important because it prepares the solution for the subsequent addition of silver nitrate, which will react with any halides present to form a precipitate.

5. **Formation of Precipitates**: After acidification, when silver nitrate is added to the sodium extract, it reacts with any halide ions (like Cl⁻, Br⁻, or I⁻) to form insoluble silver halides (AgCl, AgBr, AgI), which appear as white precipitates.

### Conclusion:
The correct answer to the question is that boiling the sodium extract with concentrated nitric acid serves to:
- Decompose sodium cyanide and sodium sulfide (if present).
- Acidify the sodium extract.

Thus, options 2, 3, and 4 are correct.

---