Question

Fractional distillation is used when the difference in the boiling points of two liquids in a mixture is _______.

Answer 1

Fractional distillation: It is a technique for the separation of a mixture of two miscible liquids which have comparable boiling points i.e.; the difference between their boiling points is less than $25\mathrm{K}(<25\mathrm{K})$ where K= kelvin.

• Example: A mixture of Ethanol $\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\right)$ and Propanone $\left({\mathrm{CH}}_3{\mathrm{COCH}}_3\right)$ is separated by fractional distillation.

Distillation: It is a technique for the separation of a mixture of two miscible liquids which have sufficient differences (>25 K) in their boiling points.

• Example: A mixture of Propanone $\left({\mathrm{CH}}_3{\mathrm{COCH}}_3\right)$ and Water $\left({\mathrm{H}}_2\mathrm{O}\right)$ is separated by distillation.

Miscible liquids: A mixture of two or more liquids that mix with each other to form a homogeneous solution.

Therefore, fractional distillation is used when the difference in the boiling points of two liquids in a mixture is <25 K.