Describe the construction of standard hydrogen electrode.

Explanation

Standard Hydrogen Electrode: It consist of platinum wire sealed in a glass tube and has a platinum foil attached to it. The foil is coated with finely divided platinum and acts as platinum electrode. It is dipped into an solution containing `H^(+)` ions in 1M concentration (1M HCl). Pure hydrogen gas at 1 bar (Atm) pressure is constantly bubbled into solution at constant temperature of 298 K.

If S.H.E. Acts as Anode: `H_(2)(g) rarr 2H^(+) + 2e^(-)`
If S.H.E Acts as Catode: `2H^(+) + 2e^(-) rarr H_(2)(g)`
This standard hydrogen electrode in also regarded as reversible electrode: `H_(2) hArr 2H^(+) + 2e^(-)`