Atom of nitrogen

Nitrogen Gas

Symbol: N
Molecular formula: N2
Atomic number: 7
Atomic number: 14
Position in the Periodic Table: Group 5
Electronic configuration: 2, 5

Discovery

Nitrogen gas was discovered in 1772 by Daniel Rutherford, a Scottish physician and chemist. He obtained it by burning phosphorous in enclosed air. Lavoisier studied its properties in detail and showed that it does not support combustion and respiration and for this reason called azote (Greek; a = no, zoe = life).
Nitrogen is one of the gases found in nature in abundant quantity. It occupies about 78% by volume. It is also found in combined state in proteins (meat, fish, egg and pulses) and nitrate salts.
Nitrogen is an essential constituent of animal and plant life. The atmospheric nitrogen goes in cycle so that the natural balance of atmosphere air is possible. The nitrogen cycle is given below.
nitrogen cycle

Nitrogen cycle


Preparation of Nitrogen gas

From air

Nitrogen gas can be prepared from air by burning phosphorous. A small crucible is placed on a cork floating in water. The phosphorous is ignited and the crucible covered immediately by a gas jar. The oxygen present in the jar combines with phosphorous to form phosphorous pentoxide which dissolves in water and the level of water rises in the jar. The gas remaining in the jar is nitrogen.

P4 + 5O2 = 2P2O5
P2O5 + 3H2O = 2H3PO4
Nitrogen can be prepared by passing air over red hot copper which combines with the oxygen present in the air to form copper oxide and the nitrogen present can be collected over water.
preparation of nitrogen gas

Preparation of nitrogen gas


Laboratory preparation of Nitrogen gas

           

Apparatus required:

1.Round bottomed flask
2.Burner
3.Delivery tube
4.Trough
5.Beehive shelf
6.Gas jar

Chemical required

1.Ammonium chloride (NH4Cl)
2.Sodium nitrite (NaNO2)

Principle

A mixture of ammonium chloride and sodium nitrite when heated, nitrogen gas will be produced which can be collected by downward displacement of water.

            NH4Cl + NaNO2 = NaCl + N2 + 2H2O
          

  Procedure

 

Laboratory preparation of Nitrogen gas

Laboratory preparation of Nitrogen gas

The apparatus is fitted as shown in the figure. When the mixture of ammonium chloride and sodium chloride is heated it begins to decompose. Nitrogen bubbles displace water in the gas jar. Thus nitrogen gas can be collected by downward displacement of water.


Manufacture of Nitrogen gas

 

nitrogen manufactured from air

Nitrogen manufactured from air at industrial level

 

At industrial level, nitrogen is manufactured from air. Air is a mixture of different gases where nitrogen has higher percentage by volume. This nitrogen can be separated from air.
Atmospheric air is cooled down so that all gases are liquefied. The liquid air is cooled down so that nitrogen boils (nitrogen has lower boiling point than other gases). Nitrogen vapour is collected in the cylinders and sent for use. 


Properties of Nitrogen gas

            Physical properties:

1.Nitrogen is a colorless, odorless and tasteless gas.
2.It is slightly lighter than air. Its density is 14 while that of air is 14.4.
3.It is insoluble in water.
4.It is non-poisonous but animals die in an atmosphere of nitrogen for want of oxygen.

Chemical properties:

1.It is neutral to litmus.
2.Nitrogen is incombustible and a non-support of combustion but burning magnesium or aluminium continues burning in an atmosphere of nitrogen forming nitrides.
3Mg + N2 = Mg3N2
2Al + N2 = 2AlN
3.With oxygen it combines only in the presence of lighting discharge or when the mixture is passed through an electric arc.
N2 + O2 = 2NO
4.With hydrogen it combines under pressure (200 atmospheres) and in the presence of catalyst (finely divided iron + molybdenum at 500◦C).
N2 + 3H2 = 2NH3

Use of Nitrogen gas

1.Nitrogen gas is used to prepare Ammonia, nitric acid and explosives.
2.Nitrogen gas is used in aeroplane to prevent formation of explosive mixture by combination of fuel and atmospheric air.