Explain about the different industrial preparation of hydrogen.

Explanation

In the large scale, hydrogen is produced currently by steam reforming of hydrocarbons. Steam and methane reacts with each other in the presence of nickel catalyst at 35 atm and at a temperature of `800^(@)C` gives hydrogen.
`CH_(4(g))+H_(2)O_((g))toCO_((g))+3H_(2(g))`
Steam is passed over a red hot coke to produce carbon monoxide and hydrogen.
`C_((s))+H_(2)O_((g))tounderset(water)underbrace(CO_((g))+H_(2(g))`
Water gas Water is reduced to hydrogen with carbon monoxide by passing over iron oxide catalyst at `400^(@)C`
.`CO_((g))+H_(2)O_((g))toCO_(2(g))+H_(2(8))`
Hydrogen is produced as a by-product in oil refining industry during the cracking of long chain hydrocarbons.
`C_(6)H_(12(g))toC_(6)H_(6(g))+3H_(2(g))`
Hydrogen is also obtained in the manufacture of chlorine and sodium hydroxide via electrolysis of a concentrated solution of sodium chloride.