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

Question

UnlockIAS · Accepted Answer

Correct — C, Butane. LPG (Liquefied Petroleum Gas) is a mixture of light hydrocarbons obtained from petroleum refining and natural-gas processing, and its principal components are butane (C4H10) and propane (C3H8). In Indian domestic cooking-gas cylinders butane is the major constituent (blended with propane), which is why 'Butane' is the correct choice among the options given. These gases liquefy easily under moderate pressure, so a large amount of fuel can be stored as liquid in a portable cylinder.

Why the other options are wrong — (a) Wrong — hexane (C6H14) is a liquid at ordinary temperature and pressure and is a component of petrol/solvents, not of the gaseous LPG blend.  (b) Wrong — pentane (C5H12) is essentially a volatile liquid at room temperature; it is not a main constituent of LPG, which is dominated by the lighter butane and propane.  (d) Wrong — methane (CH4) is the main constituent of natural gas / CNG (compressed natural gas), NOT of LPG. This is the classic trap: LPG (petroleum gas, butane+propane) is confused with piped/natural gas (methane).

Concept: LPG is a portable liquefied fuel made mainly of butane and propane — hydrocarbons light enough to be gases at room temperature but which liquefy under modest pressure, so they can be stored in cylinders. It is distinct from CNG/PNG (natural gas), whose main constituent is methane. An odourless gas, LPG is deliberately given a smell by adding ethyl mercaptan so leaks can be detected.

State PCS 2021 Q88 — Science & Technology PYQ with Answer

State PCS 2021 Q88 — Science & Technology PYQ with Answer