Describe the construction of standard hydrogen electrode.

Explanation

In standard hydrogen electrode, a platinum wire is coated with finely divided platinum, known as platinum black. It is sealed in a glass tube. It is dipped in aqueous solution of 1M HCl concentration. Pure `H_(2)` gas is passed constantly at 1 atm. pressure. The temperature of the solution is maintained at 298 K.
A standard hydrogen electrode can act both as anode and cathode, When it acts as anode, then molecules of `H_(2)` gas changes into `H^(+)` ions as follows :
`H_(2)(g)iff2H^(+)(aq)+2e^(-)`
The `H^(+)` ions formed, go to the solution. When it acts as cathode, the `H^(+)` ions of solution accept electrons and are reduced into `H_(2)` gas as follows: `2H^(+)(aq)+2e^(-)rarrH_(2)(g)`