NaOH is prepared by the electrolysis of:
(a) aqueous solution of sodium chloride with platinum electrodes
(b) molten sodium chloride with graphite anode and iron cathodes
(c) sodium carbonate with platinum electrodes
(d) sodium carbonate with nickel electrodes
When aquous sodium chloride undergo electrolysis in presence of platinum electrodes, the reaction is follows-
NaCl ---> Na+ + Cl-
H20 ---> H+ + OH-
At anode, Cl- ions are discharged in preference to OH- ions.
Cl- ---> (1/2)Cl2 + e-
At cathode, H+ ions are discharged in preference to Na+ ions.
H+ + e- ---> (1/2)H2
Overall reaction is -
NaCl + H20 ---> Na+ + OH- + (1/2)H2 + (1/2)Cl2