Given below are two statements: 

Assertion (A): Electrolysis of NaCl solution gives chlorine at anode instead of O2 .
Reason (R): Formation of oxygen at anode requires overvoltage.

1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. (A) is false but (R) is true.

Hint: The overall reaction is as follows:
NaCl(aq) + H2O(l) → Na+(aq) + OH (aq) + 12H2(g) + 12Cl2 (g)
Electrolysis of NaCl is represented by the following chemical reactions
At cathode H+aq+e-12H2g
At anode   Cl-aq12Cl2+e-;    E°cell =1.36V
              2H2O(aq)O2(g)+4H+(aq)+4e- ;        Ecell°=1.23V
E0cell for this reaction has a lower value but the formation of oxygen at anode requires over potential.