State the use of hydrogen –

(a) As a fuel

(b) In hydrogenation of oil & coal

(c) In extraction of metals

(a) As a fuel — Hydrogen is used in the form of coal gas, water gas and liquid hydrogen.

(b) In hydrogenation of oil & coal — Vegetable oil [palm oil] turns to semi solid fats [vegetable ghee] in the presence of platinum or nickel catalyst under high pressure at about 200°C by hydrogenation.
Passage of hydrogen under high pressure over powdered coal in presence of catalyst and at a suitable temperature produces a product similar to petroleum.

(c) In extraction of metals — Hydrogen when passed over heated metals oxides of less active metals like zinc, iron, lead and copper reduces the oxides of the metals to free metals.