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_2O 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_2` but this mixture also contain small amount of hydrocarbon. Electrolysis of `H_2O` is best method formation of 99.97% pure `H_2`.
`{:("At the cathode ",:,2H_2O + 2e^(-) to 2OH^(-) + H_2),("At the anode ",:,2OH^(-) to 2H_2O + 1/2 O_2 + 2e^(-)),("Overall reaction ",:,H_2O to H_2 + 1/2 O_2):}`