Zinc metal and hydrochloric acid react to produce zinc ions, hydrogen gas and chloride ions.
Hydrogen gas is evolved as a by product of brine electrolysis which produces caustic soda.
The process of conversion of coal into a mixture of carbon monoxide and water is called coal gasification.
Carbon monoxide reacts with water vapour at temperature 450 K − 550 K in the presence of an oxide of iron to form carbon dioxide and hydrogen gas. The above reaction is called water gas shift reaction.