Answer to Question #93393 in General Chemistry for belle

Question

describe the electrolysis of dilute sodium hydroxide

Answer 1

Cathode:

  2H₂O +2e^- -> H₂ + 2OH^-

Anode:

2OH^-- 2e -> 1/2 O₂ + H₂O

Overall reaction:

H₂O -> H₂+ 1/2 O₂

Or

 2H₂O -> 2 H₂+ O₂

During the electrolysis of aqueous solutions of sodium hydroxide, water decomposes with the 

formation of gas-hydrogen and oxygen. Because sodium is an active metal, the standard 

electrode potential of a pair of Na/Na+

is -2.71 V, which is much less than the potential of 

hydrogen standard electrode, for this reason, water is decomposed at the cathode and 

hydrogen is reduced. At the anode, the process of oxidation of hydroxide ions is in progress, 

because sodium hydroxide gives an alkaline environment.