Compound A is prepared by the electrolysis of aqueous solution of B using Castner- Kellner cell with mercury as cathode and carbon as anode. A and B respectively are

Step-by-step solution

In Castner - Kellner cell, Reaction at anode is Cl ⁻ 1 2 Cl ₂+e⁻ Reaction cathode is aligned Na ⁺+e⁻ & Na 2 H ₂ O +2 e⁻ & 2 OH ⁻+ H ₂ aligned Hence, in Castner-Kellner cell NaOH is produced by NaCl solution. Hence, option (a) is correct.