Preparation of Nitrogen
The most abundant source of Nitrogen is natural air.
The air around us is composed of 78% Nitrogen, 21% Oxygen and 1% of other gases.
Hence, Nitrogen is obtained commercially by fractional distillation of liquefied air.
First, the air is liquefied by subjecting it to high pressure.
Then, the liquefied air is passed through the fractional distillation column.
Now, the boiling point of Nitrogen is 77.2 K. While the boiling point of Oxygen is 90 K.
Thus, the boiling point of Nitrogen is lesser, it distills out first and Oxygen is left behind.
This is how we obtain Nitrogen from the natural air.
However, Nitrogen can also prepared artificially.
To prepare pure Nitrogen in the laboratory, a mixture of Ammonium Chloride and Sodium Nitrite is heated.
The first product formed in this reaction is Ammonium Nitrite.
But it is very unstable and immediately breaks down into Nitrogen and Water.
Hence, the overall reaction can be given as shown above
Small amounts of Nitric acid and Nitric Oxide are also formed during this reaction.
These impurities can be removed by passing the Nitrogen gas through aqueous Sulphuric acid containing Potassium Dichromate.
Another method to prepare Nitrogen gas is the thermal decomposition of Ammonium Dichromate.
The reaction can be given as this.
Purest form of Nitrogen can also be obtained by Thermal Decomposition of Sodium or Barium Azide.
The reaction is as shown
Thus, Nitrogen can be prepared by several methods.
Commercially Nitrogen gas is obtained by fractional distillation of liquid air.
In laboratory Nitrogen gas is prepared by treating aqueous solution of Ammonium Chloride with Sodium Nitrite.
Nitrogen gas is also obtained by Thermal Decomposition of Ammonium Dichromate.
Purest form of Nitrogen gas is obtained by Thermal Decomposition of Sodium or Barium Azide.