Which one of the following is the main constituent of LPG?

1. A

   Hexane

   Hexane (C6) is a liquid petrol-range hydrocarbon, not the main constituent of domestic LPG. LPG is bottled as a liquefied C3–C4 mix. Hexane would not behave as household cooking gas under cylinder pressure.

2. B

   Pentane

   Pentane (C5) is used in some foams and as a solvent; it is not the principal LPG component. LPG specification centres on butane and propane. Pentane is one carbon too heavy for the usual LPG blend.

3. C

   Butane

   (c) Official key: The main constituent of LPG (liquefied petroleum gas) as used in Indian domestic cylinders is butane, typically with propane. Methane is natural gas (CNG/PNG); hexane and pentane are heavier fractions. Among the four alkanes listed, butane is the keyed main constituent.

4. D

   Methane

   Methane is the chief constituent of natural gas (CNG), not of LPG. Mixing methane with LPG is the standard fuel-gas confusion in prelims. The keyed LPG component here is butane.

Summary. Official key is (c). LPG for cooking is essentially liquefied butane (with propane). Methane is pipeline/CNG natural gas; pentane and hexane are heavier liquids. The question asks the main LPG constituent among four alkanes. The keyed answer is butane.