Write an essay on the commericial preparation of dihydrogen. Give balanced equations.

Explanation

Commercially hydrogen is prepared by the following methods.
(1) Electrolysis method: electrolysis of acidified or alkaline water gives hydrogen.
`2H_(2)O(l) underset("Little acid or base")overset("Electrolysis")(rarr) 2H_(2)(g)+O_(2)(g)`
(2) It is obtained as a byproduct during the manufacture of sodium hydroxide.
`NaCl rarr Na^(+) + Cl^(-)`
`H_(2)O rarr H^(+) + OH^(-)`
`2Cl^(-) rarr Cl_(2)` at anode
`{:(2H^(+)+2e^(-),rarrH_(2)),(Na^(+)+OH^(-),rarr NaOH)}` at cathode
(3) By passing a mixture of steam and hydrocarbons over a catalyst gives a mixtrue of CO and `H_(2)`.
`CH_(4) + H_(2)O rarr CO + 3H_(2)`
`C_(n)H_(2n+2) + nH_(2)O rarr nCO+(2n+1)H_(2)`
(4) When steam is passed over red hot coke water gas is formed.
`C + H_(2)O rarr CO + H_(2)`
The hydrogen present in water gas obtined from hydrocarbons and steam or coke and steam is separated by water gas shift reaction. The water gas is mixed with steam and passed over iron chromate catalyst. Then CO converts into `CO_(2)` which is removed by scrubbing with sodium arsenate.
`CO + H_(2)O rarr CO_(2) + H_(2)`.