Question

Give reason for the following

A fractionating column is used in the fractional distillation of liquid mixtures

Answer 1

Fractional distillation

• Miscible liquids having boiling point difference less than ${25}^{\mathrm{o}}\mathrm{C}$ are separated using fractional distillation
• The main difference between simple distillation and fractional distillation is the presence of fractionating column (glass beads packed in the tube)
• This provides increased surface area for continuous evaporation and condensation.
• The mixture is heated in a distillation flask, the liquid gets vaporised and condensed and one with a higher boiling point falls into the distillation flask while the one with a lower boiling point passes through the condenser and is collected in the receiver.
• After this, when the temperature increases, liquid with higher boiling point rises, condenses, and gets collected.
• So the fractionating column provides the increased surface area for continuous evaporation and condensation.
• E.g. Mixture of alcohol (boiling point $78.5^{\mathrm{o}}\mathrm{c}$) and water (${100}^{\mathrm{o}}\mathrm{c}$) is separated using this technique.