(a). What is standard hydrogen electrode?
(b). Give the reactions that occurs at this electrode wen it acts as positive in an electrochemical cell.

Explanation

(a). It is the reference electrode, in which hydrogen gas at 1 bar pressure is passed in to 1 M HCl at 298 K in which a foil of platinum coated with platinum black remains immersed.
(b). `2H^(+)(aq)+2e^(-)toH_(2)(g)` is reaction taking place, when it acts as positive electrode.