Give reason for the fact that liquid hydrogen is used as a fuel.

Using H₂ as a fuel has two major advantages:
(i) Heat of combustion of H₂ is by far the largest, i.e. 115 megajoules per kilogram (MJ/kg):
(ii) Exhaust is free from pollutants.
The most effective means of storing hydrogen is in the liquid form. The liquid H₂ is widely used as a rocket fuel since it gives higher thrusts than most of the other fuels. The range of supersonic aircraft could be increased if the aircraft used liquid H₂ as a fuel. Further hypersonic aircraft would also become possible if liquid H₂ is used as a fuel.