Uses of Dihydrogen:
(i) The largest single use of dihydrogen is in the synthesis of ammonia which is used in the manufacture of nitric acid and nitrogenous fertilizers.
(ii) Dihydrogen is used in the manufacture of vanaspati fat by the hydrogenation of polyunsaturated vegetable oils like soya bean, cotton seeds etc.
(iii) It is used in the manufacture of bulk organic chemicals, particularly methanol.
CO (g) + 2H2(g) →CH3OH(l)
(iv) It is widely used for the manufacture of metal hydrides.
(v) It is used for the preparation of hydrogen chloride, a highly useful chemical.
(vi) In metallurgical processes, it is used to reduce heavy metal oxides to metals.
(vii) It is used as a rocket fuel in space research.
(viii) It does not produce any pollution and releases greater energy per unit mass of fuel in comparison to gasoline and other fuels.

It is used in synthesis of ammonia by haberss process which is used in manufacture of nitric acid and nitrogenous fertilizersManufacture of vanaspathi fat by the hydrogenation of oilsIt is used in manufacture of bulk organic chemicals particularly methanolIt is used for manufacture of metal hydridesIt is used in the preparation of hydrogen chlorideIt is used in metallurigical process,it is used to reduce heavy metal oxides to metalsIt is used for cutting and welding purposesIt is used as a rocket fuel in space research Hydrogen is used in fuel cells for generating electric energy