Question

Assertion: Alkenes are called Olefins.
Reason: Oily liquids are formed when they react with Chlorine gas.
A) Both assertion and reason are correct and reason is the correct explanation for assertion.
B) Both assertion and reason are correct but reason is not the correct explanation for assertion.
C) Assertion is correct but reason is incorrect.
D) Both assertion and reason are correct.

Answer 1

Hint:We know that alkenes belongs to the family of hydrocarbons and it consists of a carbon-carbon double bond. They are also known as unsaturated hydrocarbons. The general formula of alkene is ${C_n}{H_{2n}}$ so, the first compound in the series of alkenes would be ethene or ethylene with the formula of ${C_2}{H_4}$ .


Complete solution:
Unsaturated hydrocarbons include alkenes and alkynes which have double and triple bond respectively.they are nonpolar and may have long chains of repeated units which are known as hydrocarbon chains.these chains ,being non polar ,are insoluble in water and act as an oil layer when mixed with water. Olefins are also known as alkenes and they are made up of hydrogen and carbon containing one or more pairs of carbon atoms. These carbon atoms are linked through a double bond.
Alkenes are known as Olefins because ethylene, which is the first member in the series of alkene also known as ethene was found to yield oily products when they were made to react with chlorine and bromine.
Because of long fatty chains of hydrocarbons these olefins are also used in surfactants and detergents; where they play the role of hydrophobic entities.
So, both the assertion and reason are correct and reason is the correct explanation for assertion.

Hence the option A is the correct answer.


Note:Olefins which contain two to four carbon atoms in a molecule are in a gaseous state at ordinary temperature and pressures while those olefins which contain five or more carbon atoms in a molecule are usually liquid at room temperature. Also, olefins are slightly soluble in water.