When dil.`HNO_(3)` is electrolysed

Options

A. `H_(2)(g)` is formed at anode
B. `O_(2)` gas is formed at anode
C. `NO_(2)` is formed at anode
D. `N_(2)` is formed at anode

Answer

To solve the question regarding the electrolysis of dilute HNO₃, we will follow these steps:

### Step 1: Identify the components in dilute HNO₃
When dilute nitric acid (HNO₃) is electrolyzed, it dissociates into ions:
\[ \text{HNO}_3 \text{(aq)} \rightarrow \text{H}^+ \text{(aq)} + \text{NO}_3^- \text{(aq)} \]

Additionally, water (H₂O) also dissociates:
\[ \text{H}_2\text{O} \text{(l)} \rightarrow \text{H}^+ \text{(aq)} + \text{OH}^- \text{(aq)} \]

### Step 2: Identify the ions present
From the above dissociation, we have the following ions in solution:
- H⁺ (hydrogen ions)
- NO₃⁻ (nitrate ions)
- OH⁻ (hydroxide ions)

### Step 3: Determine the reactions at the electrodes
- **At the Cathode (negative terminal)**: Cations (H⁺) are reduced. The reduction reaction is:
\[ 4 \text{H}^+ + 4 \text{e}^- \rightarrow 2 \text{H}_2 \text{(g)} \]
This means hydrogen gas (H₂) is produced at the cathode.

- **At the Anode (positive terminal)**: Anions (OH⁻) are oxidized. The oxidation reaction is:
\[ 4 \text{OH}^- \rightarrow 2 \text{H}_2\text{O} + \text{O}_2 + 4 \text{e}^- \]
This means oxygen gas (O₂) is produced at the anode.

### Step 4: Summarize the products formed
From the reactions:
- At the cathode, hydrogen gas (H₂) is produced.
- At the anode, oxygen gas (O₂) is produced.

### Step 5: Analyze the options given in the question
Based on the reactions:
- H₂ is formed at the cathode (not at the anode).
- O₂ is formed at the anode.
- No nitrogen gas (N₂) is produced.

Thus, the correct answer is that O₂ gas is formed at the anode when dilute HNO₃ is electrolyzed.

### Final Answer
When dilute HNO₃ is electrolyzed, O₂ gas is formed at the anode.

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