Question

What is the physical state of a straight-chain hydrocarbon containing three carbon atoms at room temperature?

Answer 1

Answer: Gaseous

Explanation: Straight Chain hydrocarbon having three carbon atoms is known as Propane. It molecular formula is

                                CH_{3}CH_{2}CH_{3}

Inter molecular forces of attraction that is London Dispersion Forces existing between its molecules are weaker that is why the propane is gaseous in nature at room temperature.

It is also used in LPG. Boiling Point of propane is -42°  C.

Answer 2

The straight-chain hydrocarbon containing three carbon atoms is propane. It's molecular formula is C3H8. 

Following is the structure of propane
                                                         CH3-CH2-CH3

Boiling point of propane is -42 oC, this suggest that propane is gas at room temperature.