Question

How will you separate the components of air?

Answer 1

Separating the components of air:

• Clean air is a homogeneous mixture of gaseous components like Nitrogen $\left({\mathrm{N}}_2\right)$, Oxygen $\left({\mathrm{O}}_2\right)$ and Argon $\left(\mathrm{Ar}\right)$.
• These gases can be separated by using the technique of fractional distillation.

Fractional distillation: It is a technique for the separation of a mixture of two miscible liquids which have comparable boiling points i.e.; the difference between their boiling points is less than 25 K.

• As components of air to be separated have a difference of less than 25 K, fractional distillation is preferred.
• So, gaseous components of air are first converted into liquid air by the process of liquefaction of gases in which gases are converted into their liquid form.

This is done by a combination of two methods:

• Increasing the pressure- This process causes heating up the air.
• Decreasing the temperature- This hot air is then allowed to pass through a chamber of freezing cold water that cools the gas and converts it into liquid air.

As the temperature starts lowering below $0°\mathrm{C}$ to liquefy the gases, Carbon dioxide $\left({\mathrm{CO}}_2\right)$ is also separated as dry ice and water vapours $\left({\mathrm{H}}_2\mathrm{O}\right)$ as ice and separated via a separator chamber. The liquid air is further pushed into the fractional distillation column.

• This cold liquid air is passed through a fractional distillation column.
• The temperature is gradually increased.
• On increasing the temperature gradually, first the vapours of the gas with the lowest boiling point are distilled over i.e.; Nitrogen with boiling point $-196°\mathrm{C}$ and is obtained at the top of the fractional distillation column as the vapours of other gas do not reach the top of the column.
• As temperature increases more, Argon gets distilled over with the boiling point of $-186°\mathrm{C}$ which is more than Nitrogen and lesser than Oxygen and gets separated at a height below Nitrogen.
• Lastly, Oxygen gets separated through fractional distillation which has the highest boiling point of $-183°\mathrm{C}$.