Question

Which compound has the lowest boiling point?
A. Ethane
B. Ethene
C. Ethyne
D. All have approximately equal boiling points.

Answer 1

Hint: The temperature at which a liquid's vapour pressure equals the atmospheric pressure of the liquid's environment is known as the boiling point. The liquid turns into a vapour at this temperature.

Complete Step By Step Answer:
The boiling point of ethane is $184.5K$ , ethene is $171K$ and ethyne is $198K$respectively. Alkynes have higher boiling points than alkanes or alkenes, because the electric field of an alkyne, with its increased number of weakly held $\pi $ electrons, is more easily distorted, producing stronger attractive forces between molecules.
Each alkene has a boiling point that is remarkably similar to an alkane with the same number of carbon atoms. At room temperature, ethene, propene, and the different butenes are gases. All of the remaining items are likely to be liquids. The boiling point of alkenes is determined by their molecular mass (chain length).
Hence, the correct option is C. Ethyne.

Additional Information:
Fuels made of hydrocarbons are commonly used. LPG (liquefied petroleum gas) and CNG (compressed natural gas) are two examples (Liquefied natural gas). They are employed in the production of polymers like polyethene and polystyrene. As a starting material, these organic compounds are used in the production of pharmaceuticals and colours. They are used as lubricants and grease.

Note:
Alkanes are a group of chemicals that possess single covalent bonds between carbon and hydrogen atoms. This group of chemicals is made up of solitary covalent connections between carbon and hydrogen atoms. The alkenes are a prevalent hydrocarbon family found in crude oil. There is at least one carbon–carbon double bond in this family. Unsaturated hydrocarbons with one triple bond are known as alkynes. The acetylenic bond is the name for the triple bond.