Which lists straight-chain alkanes from lowest to highest boiling point?
butane, hexane, propane, octane
ethane, pentane, heptane, octane
methane, nonane, butane, octane
decane, hexane, butane, propane

ethane, pentane, heptane, octane

Explanation: Boiling point is the temperature at which vapor pressure of the liquid becomes equal to atmospheric pressure.

Boiling point depends on the strength of inter molecular forces. The molecules of hydrocarbons are bonded through weak vanderwaal's forces. As the length of carbon chain increases, the surface area increases and thus the vanderwaal forces increases, thus more heat is to be supplied to break the bonds and thus there is an increase in the boiling point.