Question

Two statements, one Assertion and the other Reason, are given. Choose the correct option.
Assertion: During the electrolysis of aqueous NaCl, \( Cl_2 \) is liberated at the anode in preference to \( O_2 \) and water gets reduced to \( H_2 \) at cathode.
Reason: The reaction at anode with lower oxidation potential is not preferred due to over potential of oxygen.

• A. Both Assertion and Reason are incorrect.
• B. Both Assertion and Reason are correct.
• C. Assertion is correct but Reason is incorrect.
• D. Assertion is incorrect but Reason is correct.

Hint:

In electrolysis, actual product depends not only on electrode potential but also on overpotential and kinetics.

Answer 1

The Correct Option is B

Step 1: Analyze the assertion.
In electrolysis of aqueous NaCl (brine), at anode both \( Cl^- \) and water can be oxidized.
However, \( Cl_2 \) is liberated preferentially instead of \( O_2 \).
At cathode, water is reduced to form \( H_2 \).
Thus, the assertion is correct.

Step 2: Understand anodic reactions.
Possible anodic reactions:
\[ 2Cl^- \rightarrow Cl_2 + 2e^- \]
\[ 2H_2O \rightarrow O_2 + 4H^+ + 4e^- \]

Step 3: Compare standard potentials.
Thermodynamically, oxidation of water to oxygen should be easier.
But practically, it does not occur readily.

Step 4: Role of overpotential.
Oxygen evolution has high overpotential.
This makes oxidation of water kinetically unfavorable.

Step 5: Preference of reaction.
Due to high overpotential of oxygen, \( Cl^- \) oxidation is preferred.

Step 6: Evaluate reason.
The reason correctly explains why lower oxidation potential reaction is not preferred.

Step 7: Final conclusion.
Both Assertion and Reason are correct.
\[ \boxed{\text{Both Assertion and Reason are correct}} \]