Q.Explain preparation of hydrogen using electrolysis.

Dihydrogen is prepared in the laboratory by the action of dilute acids on active metals such as zinc, or by electrolysis of acidified or alkaline water; pure water conducts electricity poorly, so a small quantity of an electrolyte such as dilute $H_2SO_4$ or $NaOH$ is added to furnish free ions and carry the current efficiently, releasing $H_2$ at the cathode and $O_2$ at the anode. Zinc also reacts directly with hot concentrated $NaOH$ solution, liberating $H_2$ and forming sodium zincate: $Zn + 2NaOH \rightarrow Na_2ZnO_2 + H_2$. On the industrial/bulk scale, dihydrogen is obtained mainly from hydrocarbons and coal. Coal gasification passes steam over red-hot coke to give water gas, a mixture of CO and $H_2$: $C(s) + H_2O(g) \xrightarrow{1270\,K} CO(g) + H_2(g)$; its hydrogen yield can be increased by mixing the water …