Explain the given reactions with the examples :

Solution:

Hydrogenation of oils : The reaction is extremely useful in the hydrogenation of vegetable oils also called edible oils e.g. ground nut oil, cotton

seed oil etc. These are also called cooking oils and are unsaturated in the sense that their molecules contain atleast one C=C bond in their

structures. Upon passing hydrogen gas through oil in the presence of nickel catalyst, the double bond changes to single bond. As a result, the

unsaturated oil changes to solid fat which is of saturated nature. Vegetable ghees such as Dalda, are of saturated nature and are formed by

catalytic hydrogenation reaction.

Oxidation reaction :

• Loss of hydrogen is known as oxidation.
• Gain of oxygen is known as oxidation.

Therefore, it is an oxidation reaction.

Substitution Reactions : Substitution reactions are also called replacement reactions and you are quite familiar with these. In organic

compounds, particularly the saturated hydrocarbons (or alkanes), these reactions are very common. One or more hydrogen atoms in the molecule

of alkane such methane get substituted by chlorine atoms when the reaction is carried with chlorine in the presence of ultraviolet sun light.

Combustion reaction :

We have seen that all combustion reactions are basically oxidation reactions carried in the presence of air or oxygen. It is not necessary that the

reactants may burn during combustion.

• Blue flame signifies complete combustion of the fuel.
• Yellow sooty flame signifies incomplete combustion of the fuel.