Question

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Describe how nitrogen can be separated from the other components of air.

Answer 1

The most common method used to separate nitrogen from air is called fractional distillation.

Fractional distillation is a method used to separate components of a liquid mixture based on their boiling point difference.

We know that air contains different gases such as Nitrogen (more than 70%) , oxygen, carbon dioxide etc.

Boiling point of nitrogen is -196^oC whereas boiling point of oxygen is -183^oC and boiling point of carbon dioxide is -78.46^oC.

We can see that the boiling point of nitrogen and oxygen is almost close, due to which a fractional column is necessary. Fractional column can be used to separate nitrogen (gas) first ], before the oxygen comes out as the column heats up.

Steps for separation of nitrogen from air:

1. Filter air to remove dust particles and unwanted matters.
2. Cool and compress gaseous air at least to a temperature of -200^oC (at this temperature, CO₂ will be frozen and can be separated as solid)
3. Now the air is liquified and the contents are liquid nitrogen and liquid oxygen.
4. Move this liquid air into a fractional distillation column.
5. Slowly heat up the column which will result in the increase of temperature.
6. When the temperature reaches -196^oC (boiling point of nitrogen) the liquid nitrogen starts to boil and changes to gaseous state and escapes out the column, from where we can collect the nitrogen gas.
7. Followed by this, When the temperature reaches -183^oC (boiling point of oxygen) the liquid oxygen starts to boil and changes to gaseous state and slowly (due to distillation column) escapes out the column, from where we can collect the oxygen gas (if needed).