Question

a) Fog and milk both are colloidal in nature. How do they differ from each other?

b) What is the function of the fractionating column in fractional distillation?

Answer 1

Colloids

• Colloids are mixtures having 1-1000 nm sized particles dispersed in a medium.
• The particles dispersed in a medium is called dispersed phase and medium in which particles are dispersed is called dispersion medium.
• Depending upon the states of dispersed phase and dispersion medium different colloids are present like emulsion, sol etc.

a) Fog and milk are examples of two types of colloids

Fog is aerosol where the dispersed phase is liquid and the dispersion medium is gas.

Milk is an emulsion where dispersed phase and dispersion medium are liquids.

b) Fractional distillation used for the separation of miscible liquids having boiling point difference greater than ${25}^{\mathrm{o}}\mathrm{C}$.The main difference between simple distillation and fractional distillation is presence of fractionating column (glass beads packed) in fractional distillation. Fractionating column i.e glass beads allow increased surface area for the hot vapour to cool and condense repeatedly.