Question

Why double bond are present in alkene

Answer 1

This is because while joining any other element or a group of element, they may have a valency of 2 which is not satisfied by a single bond. This is because in a single bond only 2 electron bonding occurs but the bonding needs to take place for 4 electrons. Hence double bonds are formed making them belong to a group called Alkenes.

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Answer 2

Hydrocarbons are compounds made from carbon and hydrogen atoms joined by covalent bonds. Alkanes are saturated - they have only single bonds. Alkenes have a double bond - they are unsaturated. Alkenes react with brown bromine water and decolourise it, but alkanes do not.

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