Question

Which lists straight-chain alkanes from lowest to highest boiling point?

Answer 1

Answer:The correct order is:

ethane, pentane, heptane, octane

Explanation:

The boiling point of the alkanes increases with increase with an molecular mass that is higher the number of carbon atoms in the alkane higher will be the boiling point of the alkane.

With increase in molecular area the surface area and association of an alkane also increases.

Ethane = $C_2H_6$, 2 carbon atoms.

Pentane =$C_5H_{10}$,5 carbon atoms.

Heptane = $C_7H_{16}$,7 carbon atoms.

Octane =$C_8H_{18}$,8 carbon atoms.

Straight-chain alkanes from lowest to highest boiling point:

ethane<pentane<heptane< octane

Answer 2

Answer: 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.