The sodium extract on acidification with acetric acid and then adding lead acetate solution gives a black precipitate. The organic compound contains.

Options

A. Nitrogen
B. Halogen
C. Sulphur
D. Phosphorus

Answer

To solve the question regarding the organic compound that gives a black precipitate upon acidification and treatment with lead acetate, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Test**:
The problem describes a process involving the sodium fusion extract, which is acidified with acetic acid and then treated with lead acetate. This is a classic test known as the Lassaigne's test, used to detect certain elements in organic compounds.

**Hint**: Remember that Lassaigne's test is used to identify elements like nitrogen, sulfur, phosphorus, and halogens in organic compounds.

2. **Identifying the Reaction**:
When the organic compound contains sulfur, it reacts with sodium to form sodium sulfide (Na2S). The reaction can be summarized as:
\[ 2 \text{Na} + \text{S} \rightarrow \text{Na}_2\text{S} \]

**Hint**: Look for the formation of sodium sulfide when sulfur is present in the organic compound.

3. **Acidification**:
The sodium sulfide (Na2S) is then acidified with acetic acid (CH3COOH). This step is crucial as it prepares the sodium sulfide for the next reaction.

**Hint**: Acidification often changes the solubility and reactivity of compounds, making them ready for further testing.

4. **Reaction with Lead Acetate**:
After acidification, the sodium sulfide is treated with lead acetate (Pb(CH3COO)2). The reaction produces lead sulfide (PbS), which is a black precipitate:
\[ \text{Na}_2\text{S} + \text{Pb(CH}_3\text{COO)}_2 \rightarrow \text{PbS (black precipitate)} + 2 \text{NaCH}_3\text{COO} \]

**Hint**: The formation of a black precipitate is a key indicator of the presence of sulfur in the organic compound.

5. **Conclusion**:
Since the test results in a black precipitate, we can conclude that the organic compound contains sulfur.

**Final Answer**: The organic compound contains sulfur (Option C).