a) State why hydrogen is said to be a clean fuel?
b) What property of hydrogen is involved in being a good fuel?
c) What is hydrogenation of oils? Write one application.

a) Hydrogen is a clean fuel because its reaction with oxygen produces only water. It does not form gases like CO₂, NO₂ etc, which pollute air.b) Hydrogen, on combustion with oxygen, produces water and a lot of heat. This is an exothermic reaction.c) Oils are unsaturated molecules, containing double bond. So hydrogen atoms are added at the double bonds of the molecules of oil. The reaction of hydrogen with oils is known as hydrogenation.
The hydrogenation reaction takes place at 473 K and in the presence of nickel catalyst.
Vanaspati or dalda ghee is prepared by hydrogenation of vegetable oils.