Question

What is the fractional distillation? Explain.

Answer 1

The fractional distillation is a separation technique of two or more miscible liquids that is based upon the principle of difference in their boiling points. Fractional distillation is a more precise technique as compared to conventional distillation.

Complete step by step answer:

The fractional distillation is the separation technique for two or more miscible liquids. If liquids in a mixture are miscible and boil without decomposition and also possess different boiling points, then that type of mixtures can be separated out by distillation process.
The basic principle of this type of distillation is that the different liquids tend to boil and evaporate at different temperatures. When the mixture is being heated, the substance having lower boiling point starts to boil first and further converts into the vapors.
Distillation involves the conversion of a liquid into vapor followed by the condensation of vapor back into the liquid. The apparatus for the fractional distillation is the same as the simple distillation, except the fractionating column is fitted in between the distillation flask and the condenser.
A simple fractionating column is a tube packed with glass beads. The beads provide surface for the vapors to cool and condense repeatedly.
Fractional distillation apparatus includes distillation flask, condenser, receiver, fractionating column thermometer and heat source. After setting up the apparatus, the mixture of miscible liquids let’s say A and B is taken. In which, A has more volatility as compared to B.
The solution is added to the distilling flask and heat is applied in which temperature is slowly raised. Component A will start vaporizing and through the fractionating column it will move to the condenser where it is cooled down to form a liquid.
Condensation takes place repeatedly until both the samples will separate out.

Note:
Distillation is used only if the liquids have a difference in boiling points of more than 25K. To separate the mixtures of two or more miscible liquids for which the differences in boiling points is less than 25 K, then the fractional distillation technique is used.
For example: Separation of different gases from the air, different fractions from petroleum products etc.