Question

how hydrogenhow is to gas is prepared in the lab ​

Answer 1

Basic gases (e.g. ammonia) can be dried with calcium oxide, sodium hydroxide or soda lime. Disposal of the gases can be done by burning the flammable ones (carbon monoxide, hydrogen, hydrocarbons), absorbing them in water (ammonia, hydrogen sulfide, sulfur dioxide, chlorine), or reacting them with a suitable reagent.

Answer 2

HEYA!
________

pure hydrogen gas can be prepared in lab by the following reaction. This is a short and sweet method.

Mg + dil⋅H2SO4 --» MgSO4 + H2↑