In Lassaigne's test for the detection of halogen , the sodium fusion extract is first boiled with concentrated nitric acid . This is

Options

A. To dissolve `Ag_(2)S`
B. To remove silver halides
C. To decompose `Na_(2)S and NaCN`, if present
D. Because `Ag_(2)S` and `AgCN` are insoluble in nitric acid

Answer

To solve the question regarding Lassaigne's test for the detection of halogens, we need to understand the purpose of boiling the sodium fusion extract with concentrated nitric acid. Here’s a step-by-step breakdown of the solution:

### Step 1: Understanding Lassaigne's Test
Lassaigne's test is a qualitative analysis method used to detect halogens (like Cl, Br, I) in organic compounds. The organic compound is fused with sodium metal, which converts halogens into sodium halides.

### Step 2: Sodium Fusion Extract
After fusion, the sodium extract contains sodium halides, sodium sulfide (Na2S), and sodium cyanide (NaCN). The presence of these compounds can interfere with the detection of halogens.

### Step 3: Purpose of Boiling with Concentrated Nitric Acid
Boiling the sodium fusion extract with concentrated nitric acid serves a specific purpose:
- It helps to decompose and remove sodium sulfide (Na2S) and sodium cyanide (NaCN) from the extract.

### Step 4: Chemical Reactions
When concentrated nitric acid (HNO3) is added to the sodium extract, it reacts with NaCN and Na2S:
- For NaCN:
\[ 3 \text{NaCN} + 4 \text{HNO}_3 \rightarrow 3 \text{NaNO}_3 + 2 \text{HCN} + \text{H}_2\text{O} \]
- For Na2S:
\[ \text{Na}_2\text{S} + 2 \text{HNO}_3 \rightarrow 2 \text{NaNO}_3 + \text{H}_2\text{S} \]

### Step 5: Conclusion
The main reason for boiling the sodium fusion extract with concentrated nitric acid is to decompose Na2S and NaCN, which are insoluble in nitric acid. This step is crucial for the accurate detection of halogens in the subsequent steps of Lassaigne's test.

### Final Answer
The sodium fusion extract is first boiled with concentrated nitric acid to decompose Na2S and NaCN if present.

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