What is the main constituent of LPG? 

Propane and butane

The correct answer is option 4. Propane and butane.

The main constituents of LPG are butane and propane. Both of them are mixed to form LPG. So, option D is the correct one. Let us know more about LPG in detail. The full form of LPG is Liquefied Petroleum Gas. Though it mainly contains propane and butane, some traces of other hydrocarbons may be present in it. The chemical formula of propane is \(CH_3CH_2CH_3\) and that of butane is\(CH_3CH_2CH_2CH_3\).  It is a fossil fuel, i.e. its main source is fossils. It is a non-renewable source of energy like all fossil fuels. A non-renewable energy source extinguishes after a certain period. LPG is extracted from natural gas and crude oil. The energy content in LPG is quite similar to petroleum. It burns very readily in the air giving out heat energy that is twice the energy given out by natural gas. This feature makes it an excellent fuel for cooking and heating purposes. This gas is called “liquefied” because it is normally stored under pressure in liquid form in containers like cylinders or tanks. The propane and butane in the LPG mix are in the gaseous phase under normal circumstances but they turn to liquid when pressure is applied. On the release of pressure, they turn into a gas again.