Aqueous solution of `NaCl` containing a small amount of `MeOH` ( methyl orange ) is electrolysed using `Pt-` electrodes . The color of the solution after some time will .

Options

A. remains yellow
B. change from yellow to colorless
C. change from yellow to red
D. remain red

Explanation

To determine the color of the solution after the electrolysis of an aqueous solution of NaCl containing a small amount of methyl orange (MeOH), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Electrolysis Process**:
- When an aqueous solution of NaCl is electrolyzed, ions present in the solution will migrate towards the electrodes. The main ions are Na⁺, Cl⁻, H⁺, and OH⁻.

2. **Identify the Electrodes**:
- The electrodes used are platinum (Pt) electrodes. At the cathode (negative electrode), reduction occurs, while at the anode (positive electrode), oxidation occurs.

3. **Movement of Ions**:
- At the cathode, both Na⁺ and H⁺ ions will move towards it. However, H⁺ ions have a lower discharge potential than Na⁺ ions, meaning H⁺ will be discharged first.
- At the anode, Cl⁻ and OH⁻ ions will move towards it. Cl⁻ ions will be discharged preferentially over OH⁻ ions due to lower discharge potential.

4. **Reactions at the Electrodes**:
- At the cathode:
\[ 2H^+ + 2e^- \rightarrow H_2(g) \]
Hydrogen gas (H₂) is liberated at the cathode.
- At the anode:
\[ 2Cl^- \rightarrow Cl_2(g) + 2e^- \]
Chlorine gas (Cl₂) is liberated at the anode.

5. **Remaining Ions in Solution**:
- After the electrolysis, Na⁺ ions and OH⁻ ions remain in the solution. The presence of Na⁺ and OH⁻ leads to the formation of sodium hydroxide (NaOH).

6. **Determine the Nature of the Solution**:
- The solution now contains NaOH, which is a strong base. This means the pH of the solution will be greater than 7, indicating a basic solution.

7. **Effect on Methyl Orange**:
- Methyl orange is a pH indicator that turns red in acidic conditions (pH < 3.1) and yellow in neutral to basic conditions (pH > 4.4). Since the solution is basic due to the presence of NaOH, methyl orange will appear yellow.

### Conclusion:
The color of the solution after some time will remain **yellow**.

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