Electrolysis of Brine

                      Electrolysis of concentrated solution of NaCl

          The electrolysis of brine results in hydrogen (H₂) and chlorine gas. It  is a large-scale process used to manufacture chlorine (Cl₂). The other useful co-product is sodium hydroxide (NaOH).

      At the cathode, water is reduced to hydroxide ion and hydrogen gas. (The more reactive a metal, the less readily its ion is reduced on the electrode surface.) 
At the anode, chloride (Cl^-) ions are preferentially oxidized to chlorine.

Reduction at Cathode :

                  2H₂O(l) + 2e^–   =   H₂(g)  + 2OH^-(aq) 

Oxidation at Anode : 
                   2Cl^–(aq)  =  Cl₂(g) + 2e^– 

Overall reaction :

     2H₂O(l)  + 2Cl^–(aq)  =  2OH^–(aq)  + H₂(g) + Cl₂(g) 
             
              (The sodium ions are spectator ions)