Question

How will you separate the mixture of two gases?
A) Fractional distillation technique
B) Graham’s law of diffusion technique
C) Osmosis
D) Chromatography

Answer 1

Hint: Gases are homogeneous mixture and components of homogeneous mixture cannot be separated easily. Hence, special techniques are required for the separation of mixture of gases. Gases first undergo liquefaction process and then are separated on the basis of their boiling points.

Complete step by step answer:
We all know that special techniques are required to separate mixtures of gases because generally, gases are homogenous mixtures. Fractional distillation is the special technique which is used for separation of mixture of two gases. Fractional distillation process separates the components of mixture into a number of fractions in increasing order of their boiling points. The mixture is introduced into a tall fractionating column and heated, which results in the separation of different fractions. More volatile fractions or components with lower boiling point are collected at the top of the column whereas the less volatile fractions having higher boiling point get collected at the bottom of the column.

Let us try to understand the fractional distillation technique in steps:
- Conversion of gases mixture into liquid:
Mixtures of gases are converted into liquid form by applying high pressure. Under high pressure, the mixture is compressed and then cooled by decreasing the temperature. This results in a liquid mixture.
- Distillation
The liquid mixture is then passed through the fractional distillation column. In this, the liquid mixture is allowed to warm-up or heat. The bottom of the fractionating column is quite warmer than the top. Each gas starts to separate at different temperatures according to their boiling points and thus, in this way mixture of two gases is separated.
So, the correct answer is “Option A”.

Note: Air is a homogenous mixture of gases and it is also separated by the fractional distillation technique. Oxygen has higher boiling point than nitrogen and thus, nitrogen being more volatile is collected at the top of the column and oxygen being less volatile is collected at the bottom of the fractionating column.