When primary amines react with nitrous acid, the gas evolved is

Options

A. `N_(2)`
B. `NH_(3)`
C. `CO_(2)`
D. `CO`

Explanation

To solve the question regarding the gas evolved when primary amines react with nitrous acid, we can break down the reaction step by step.

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The primary amines are represented as RNH2, where R can be an aliphatic or aromatic group.
- Nitrous acid is represented as HNO2.

2. **Understand the Reaction**:
- When a primary amine reacts with nitrous acid, the reaction can be summarized as follows:
\[ RNH_2 + HNO_2 \rightarrow R-N_2^+ + H_2O \]
- Here, the primary amine (RNH2) reacts with nitrous acid (HNO2) to form a diazonium ion (R-N2^+).

3. **Formation of Nitrogen Gas**:
- The diazonium ion (R-N2^+) is unstable and decomposes, releasing nitrogen gas (N2) as a byproduct:
\[ R-N_2^+ \rightarrow R^+ + N_2 \uparrow \]
- The nitrogen gas (N2) is the gas evolved during this reaction.

4. **Conclusion**:
- Therefore, the gas evolved when primary amines react with nitrous acid is nitrogen gas (N2).

### Final Answer:
The gas evolved is **N2 gas**.

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