If a straight-chain hydrocarbon is a gas at room temperature, how many carbon atoms will it have?

A. 6 carbon atoms

B. 12 carbon atoms

C. 24 carbon atoms

D. 3 carbon atoms

The fewer the carbon atoms, the closer it is to being a gas. The only one you have to check out is A which is hexane. You know that gasoline at the pumps has 8 carbons and its a liquid. So B and C are both not gases because they are above 8.

C6 (hexane) is a liquid at room temperature not a gas.

The answer is D. If there is a gas present, it must be C3