Very pure hydrogen (99.9%) can be made by which of the following processes?

Options

A. Reaction of methane with steam
B. Mixing natural hydrocarbons of high molecular weight.
C. Electrolysis of water.
D. Reaction of salt like hydrides with water.

Answer

C

Explanation

`CH_(4) + H_(2)O overset(800-900^(@)C)(rarr)CO+3H_(2)`
In this method mixture of CO and `H_(2)` are obtained. High molecular weight hydrocarbon on cracking gives H, but this mixture also contain small amount of hydrocarbon. Electrolysis of `H_(2)`O is best method formation of 99.97% pure` H_(2)`,
At the cathode : `2H_(2)O 2e^(-) rarr 2OH^(-) + H_(2) `
At the anode : `2OH^(-) rarr 2H_(2) O + (1)/(2) O_(2) + 2e^(-)`
Overall reaction : `H_(2) O rarr H_(2) + (1)/(2) O_(2)`