The gas evolved when methylamine reacts with nitrous acid is….

Options

A. `NH_(3)`
B. `N_(2)`
C. `H_(2)`
D. `C_(2)H_(6)`

Explanation

To determine the gas evolved when methylamine reacts with nitrous acid, we can follow these steps:

### Step 1: Identify the Reactants
- Methylamine (CH₃NH₂) is a primary amine, meaning it has one alkyl group attached to the nitrogen.
- Nitrous acid (HNO₂) is the other reactant.

### Step 2: Write the Reaction
When methylamine reacts with nitrous acid, a diazotization reaction occurs. The general reaction can be written as:
\[ \text{CH}_3\text{NH}_2 + \text{HNO}_2 \rightarrow \text{CH}_3\text{N}_2^+ + \text{Cl}^- \]
This forms a diazonium salt (methyl diazonium chloride).

### Step 3: Analyze the Stability of the Diazotization Product
The methyl diazonium salt formed is not stable. It will decompose when treated with water.

### Step 4: Decomposition of the Diazotization Product
Upon hydrolysis (reaction with water), the diazonium salt decomposes to form methanol (CH₃OH) and nitrogen gas (N₂):
\[ \text{CH}_3\text{N}_2^+ + \text{H}_2\text{O} \rightarrow \text{CH}_3\text{OH} + \text{N}_2 + \text{H}^+ + \text{Cl}^- \]

### Step 5: Identify the Gas Evolved
From the decomposition reaction, we can see that nitrogen gas (N₂) is produced as one of the products.

### Conclusion
The gas evolved when methylamine reacts with nitrous acid is nitrogen gas (N₂).

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