Assertion (A): Electrolysis of NaCl solution gives chlorine at anode instead of `O_(2)`.

Options

A. Both A and R are true but R is NOT the correct explanation of A
B. Both A and R are true but R is NOT the correct explanation of A
C. A is true but R is false
D. A is false and R is True

Explanation

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided.

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that during the electrolysis of a sodium chloride (NaCl) solution, chlorine gas (Cl₂) is produced at the anode instead of oxygen gas (O₂).
- In the electrolysis of NaCl solution, the ions present are Na⁺ and Cl⁻, along with water (H₂O) which also dissociates into H⁺ and OH⁻ ions.

2. **Electrolysis Process**:
- At the anode, oxidation occurs. The possible oxidation reactions are:
- Oxidation of chloride ions (Cl⁻) to chlorine gas (Cl₂).
- Oxidation of water (H₂O) to produce oxygen gas (O₂).
- The reaction for the oxidation of Cl⁻ is:
\[ 2Cl^- \rightarrow Cl_2 + 2e^- \]
- The reaction for the oxidation of water is:
\[ 2H_2O \rightarrow O_2 + 4H^+ + 4e^- \]

3. **Standard Electrode Potentials**:
- The standard electrode potential (E°) for the oxidation of Cl⁻ to Cl₂ is approximately +1.36 V.
- The standard electrode potential (E°) for the oxidation of water to O₂ is approximately +1.23 V.
- Since the E° for the oxidation of Cl⁻ is higher than that for water, Cl⁻ is oxidized preferentially to Cl₂ at the anode.

4. **Understanding the Reason (R)**:
- The reason states that the formation of oxygen at the anode requires overvoltage.
- Overvoltage is the extra voltage required beyond the theoretical value to initiate an electrochemical reaction. For the oxidation of water to O₂, the actual potential required is higher than the standard potential due to kinetic barriers.

5. **Conclusion**:
- Both the assertion (A) and the reason (R) are true. However, the reason (R) does not directly explain why chlorine is produced instead of oxygen. The assertion is based on the relative standard potentials of the reactions, while the reason discusses the practical aspect of overvoltage.

### Final Answer:
- Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.