electrolysis (nickel plating)

In electroplating of nickel, hydrogen will not given off at the cathode. Instead, the nickel ions are dischargedat the cathode, and the cathode metal is plated with a layer of nickel.

The electrolyte of the electrolysis is a solution of nickel salt, usually nickel(II)salt which dissociates in the aqueous solution to give nickel(II) ions. The self-dissociation of water gives hydrogenions and hydroxide ions.

In electrolysis, nickel(II) ions and hydrogen ions migrate to the cathode. Nickel(II) ions is preferentially discharged becausethey are much more concentrated than hydrogen ions. Nickel ions are discharged to give nickel metal,which forms a layer to plate on the cathode metal.