Following reactions may occur at cathode and anode during electrolysis of aqueous sodium chloride. What products will be held at anode and cathode ?Use given E° values to justify your answer.

Cathode : E° = -2.71V

E° = 0.00 V

Anode : E° = 1.36V

E° = 1.23V

We know that for a redox reaction to occur, the species with a higher tendency to lose electrons must lose them and those species with a greater tendency to accept electrons, gain these electrons.

At cathode, a reduction reaction with higher reduction potential is preferred. Therefore, the reaction at the cathode during electrolysis will be

And hydrogen gas is produced at cathode. This is because the reduction potential of the formation of H₂ gas (0V) is more than that of the formation of Na(s) (-2.71V).

At anode, generally, the oxidation reaction involving lower reduction potential is preferred. But here something different occurs. Due to a particular condition of overvoltage, the reaction involving oxidation of chloride ion is preferred and chlorine gas is obtained at anode.

So, overall reaction is :