Assertion: Electrolysis of NaCl solution gives chlorine at anode instead of `O_(2)`.
Reason: Formation of oxygen at anode requires overvoltage.

Options

A. Both assertion and reason are true and the reason is the correct explanation of assertion.
B. Both assertion and reason are true and the reason is not the correct explanation of assertion.
C. Assertion is true but the reason is false.
D. Both assertion and reason are false.

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states that during the electrolysis of NaCl solution, chlorine gas is produced at the anode instead of oxygen gas.

- **Electrolysis of NaCl Solution**: When NaCl is dissolved in water, it dissociates into Na⁺ and Cl⁻ ions. During electrolysis, the anode is where oxidation occurs, and the cathode is where reduction occurs.
- **At the Anode**: The anode attracts the negatively charged chloride ions (Cl⁻). When these ions reach the anode, they are oxidized to form chlorine gas (Cl₂).

### Step 2: Understand the Reason
The reason provided states that the formation of oxygen at the anode requires overvoltage.

- **Overvoltage**: This is the extra voltage that must be applied to drive a non-spontaneous reaction. In the case of water electrolysis, producing oxygen gas at the anode typically requires a higher voltage than what is needed for the oxidation of chloride ions.
- **Preference for Chlorine Production**: Since the oxidation of Cl⁻ to Cl₂ occurs at a lower potential than the oxidation of water to O₂, chlorine is produced preferentially at the anode during the electrolysis of NaCl solution.

### Step 3: Conclusion
Both the assertion and the reason are true. The assertion correctly states that chlorine is produced at the anode instead of oxygen, and the reason correctly explains that the formation of oxygen requires overvoltage, making chlorine production more favorable.

### Final Answer
- **Assertion**: True
- **Reason**: True
- **Conclusion**: The assertion is correct, and the reason provided supports the assertion.