Which hydrocarbon is an unsaturated hydrocarbon? A. 2-methylheptane B. 3-ethylpentane C. 1-hexene D. cyclopentane

Answer: - C) 1-hexene

Solution: - There are two types of hydrocarbons, saturated and unsaturated. Saturated hydrocarbons are those having with all single covalent bonds between carbons. The suffix - ane is used for naming these compounds. For example ethane, propane etc. Unsaturated hydrocarbons are those having with double or triple covalent bonds between carbons. There might be one or more multiple bonds. The suffix used for naming hydrocarbons having double bonds is - ene (examples: - Ethene, propene, butene etc) and for triple bonds it is - yne (examples:-. Ethyne, Propyne, 1-Butyne etc)

The first given name is 2-methylheptane. Here the ending is - ane means all single bonds between carbons and so it is saturated hydrocarbon.

Second given name is 3-ethylpentane. Here also, the ending is - ane means it is also saturated hydrocarbon. Third given name is 1-hexene. Here, the ending is - ene means double bond between two carbons (first and second carbons) so it is unsaturated hydrocarbon. Fourth given name is cyclopentane. Here, the ending is - ane and so it is saturated hydrocarbon.

So, the only correct choice is C) 1-hexene.