Question

How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25$^ \circ C$), which are miscible with each other?

Answer 1

Hint: Since the question mentions the large difference in boiling point we will use a method which will first separate the component having lower boiling point and then the component having higher boiling point by boiling the mixture.

Complete step by step answer:
-Since the question says that kerosene and petrol are miscible with each other and the difference in their boiling points is more than 25$^ \circ C$ which is a large difference and so they can be separated by the process of simple distillation.
-Simple distillation is basically a common technique used for the purification of organic compounds. It separates volatile liquids from non-volatile impurities and liquids having large differences in their boiling points. The compounds having lower boiling points get evaporated first. The vapours formed are then cooled and the liquids so formed are separately collected.

-The liquid mixture which needs to be purified is taken in a round bottom flask which is then heated slowly and carefully. On heating the mixture begins to boil in some time and the component having a lower boiling point will start evaporating first. Its vapours are then condensed using a condenser and the liquid formed is collected in the receiver. The component which has the highest boiling point forms vapours at the last and thus can be collected separately.
For example: Chloroform ($CHC{l_3}$) having a boiling point of 334K can be separated from aniline (${C_6}{H_5}N{H_2}$) which has a boiling point of 457K via distillation.

-So, since the difference between boiling point of kerosene and petrol is more than 25$^ \circ C$ they can be separated by distillation. The mixture of kerosene and petrol will be put in a distillation flask which is being heated. As the temperature of the mixture rises we will notice that first petrol will evaporate and form vapours since it has a lower boiling point. The vapours of petrol are condensed using a condenser and collected through the condenser outlet. Kerosene having a higher boiling point will be left behind in the distillation flask.

Note: If the difference in boiling points of 2 liquids is not high, a simple distillation process cannot be used for their separation because their vapours will be formed within the same temperature range. Such liquids are separated by fractional distillation by passing the vapours through a fractionating column before their condensation.