If Pt is used as cathode in the electrolysis of aqueous NaCl solution, the ion reduced at cathode is :

Options

A. `H^+`
B. `Na^+`
C. `OH^-`
D. `Cl^-`

Answer

To solve the question of which ion is reduced at the cathode during the electrolysis of an aqueous NaCl solution using a platinum electrode, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Electrolyte Components**:
- When NaCl is dissolved in water, it dissociates into sodium ions (Na⁺) and chloride ions (Cl⁻). Additionally, water (H₂O) also dissociates into hydrogen ions (H⁺) and hydroxide ions (OH⁻).

2. **Determine the Ions Present**:
- The ions present in the solution are Na⁺, Cl⁻, H⁺, and OH⁻.

3. **Understand the Process at the Cathode**:
- The cathode is negatively charged, which attracts positively charged ions. Therefore, Na⁺ and H⁺ ions will migrate towards the cathode.

4. **Consider the Reduction Reactions**:
- At the cathode, reduction occurs. The possible reduction reactions are:
- Na⁺ + e⁻ → Na (sodium metal)
- 2H⁺ + 2e⁻ → H₂ (hydrogen gas)

5. **Evaluate the Feasibility of Each Reaction**:
- Sodium (Na) is a metal and has a strong tendency to oxidize (lose electrons). Therefore, the reduction of Na⁺ to Na is not favorable under these conditions.
- On the other hand, the reduction of H⁺ to H₂ is more favorable and occurs more readily.

6. **Conclusion**:
- Since the reduction of sodium ions is not feasible, the ion that will be reduced at the cathode is H⁺, resulting in the formation of hydrogen gas (H₂).

### Final Answer:
The ion reduced at the cathode is **H⁺** (hydrogen ion).

---