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)`

Answer

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

### Step 1: Identify the Reactants
The reactants in this reaction are methylamine (CH₃NH₂) and nitrous acid (HNO₂).

### Step 2: Understand the Reaction Conditions
The reaction takes place in an acidic medium, typically with hydrochloric acid (HCl) present, and at a low temperature (0 to 5 degrees Celsius).

### Step 3: Formation of the Diazonium Salt
When methylamine reacts with nitrous acid, it forms an alkyl diazonium salt. The reaction can be represented as follows:
\[ \text{CH}_3\text{NH}_2 + \text{HNO}_2 \rightarrow \text{CH}_3\text{N}_2^+\text{Cl}^- \]
This results in the formation of methyl diazonium chloride.

### Step 4: Hydrolysis of the Diazonium Salt
In the presence of water (H₂O), the diazonium salt undergoes hydrolysis. The nitrogen in the diazonium salt is positively charged, and the reaction proceeds as follows:
\[ \text{CH}_3\text{N}_2^+\text{Cl}^- + \text{H}_2\text{O} \rightarrow \text{CH}_3\text{OH} + \text{N}_2 + \text{HCl} \]
Here, the nitrogen gas (N₂) is evolved as a product.

### Step 5: Identify the Evolved Gas
From the hydrolysis of the diazonium salt, we see that nitrogen gas (N₂) is produced. Therefore, the gas evolved when methylamine reacts with nitrous acid is nitrogen.

### Final Answer
The gas evolved when methylamine reacts with nitrous acid is **Nitrogen (N₂)**.

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