PREPARATION OF NITROGEN
The only important commercial method of producing nitrogen gas is the fractional distillation of liquid air. In this process air is first liquefied to form fractional air, which is then fractional distilled. Air liquifed by successive compression and expansion.
Fractional Distillation of Liquid Air:
Clean air is compressed and then cooled by refrigeration, upon expanding the air, the air further cools and liquefies. The liquid air is filtered to remove carbon dioxide solid and then distilled. Nitrogen is the most volatile component, with boiling point -196 °C, distill over. Arogon which boils at -185.7°C, is removed from the middle of the column and liquid oxygen, the least volstile
(b): In laboratory
Pure nitrogen in the loboratry is prepared by heating ammonium nitrite which thermally decomposes to give nitrogen gas. Ammonium nitrite is first obtained by reacting ammonium chloride with sodium nitrite.
- Formation of ammonium nitrite
NH4CL+NaNO2 _ NH4NO2+NaCL
- Preparation of N2
NH4NO2 _ N2+2H2O
- Nitrogen is a colourless, odourless and tasteless gas.
- Pure nitrogen is slightly soluble in water. Two volumes of the gas dissolves in 100 volumes of water at room temperature.
- It is slightly lighter then air.
- Its boiling point is -196°C, while menlting point is -210°C
Molecular nitrogen is unreactive because of strong triple bond between two nitrogen atoms ,The bonf enthalpy i.e. the bound dissociation energy of N2 is about 941 KJ/mol which is very high. When substances normally burn in air, they combine with oxygen only, althoungh air contains 78% nitrogen by volume. However at very high temperatures and pressures, nitrogen combines directly with hydrogen, oxygen and metals linke maganesium to form compounds.