Dinitrogen
Preparation of Nitrogen
Laboratory Preparation :
- Reaction of Aqueous solution of Ammonium Chloride with Sodium Nitrite $$ce{NH4Cl (aq) + NaNO2 (aq) -> N2(g) + 2H2O (l) + NaCl (aq)}$$
- Thermal decomposition of Ammonium Dichromate; $$ ce{(NH4)2Cr2O7 ->[heat] N2(g) + 4H2O + Cr2O3} $$
- Thermal decomposition of sodium or barium azide (very pure form of nitrogen); $$ce{Ba(N3)2 ->[heat] Ba + 3N2}$$ $$ce{2NaN3 ->[heat] 2Na + 3N2}$$
In the reaction of Ammonium Chloride with Sodium Nitrite, small amount of (ce{NO}) and (ce{HNO3}) are also produced. These impurities are removed by passing the gas through aqueous sulphuric acid containing potassium dichromate, (ce{K2Cr2O7}).
Commercial Production of Dinitrogen
Liquefaction and fractional distillation of air. Liquid dinitrogen (b.p. 77.2 K) distils out first. Remain contains liquid oxygen (b.p. 90 K).
Properties
Physical Properties
- Odourless, colourless, tasteless, non-toxic gas
- Isotopes – Nitrogen-14 and Nitrogen-15
- very low solubility in water
- low freezing and boiling point
Chemical Properties :
- Chemically inert at room temperature due to high bond enthalpy of (ce{N#N}) bond.
- Rapid increase in reactivity with rise in temperature
- Reaction with metals at higher temperature, $$ce{Nitrogen + Metal ->[heat] Ionic Metallic Nitride}$$ $$ ce{6Li + N2(g)->[Heat] 2Li3N}$$ $$ce{3Mg + N2(g) ->[Heat] Mg3N2}$$
- Reaction with non-metals at higher temperature, $$(ce{Nitrogen + non-Metal ->[heat] Covalent Nitrides})$$
- At 773 K and in presence of catalyst, it forms ammonia (Haber’s Process) on reaction with (ce{H2}); $$ce{N2(g) + 3H2(g) <=>[773 K] 2NH3(g)}$$
- At very high temperature, nitrogen reacts with oxygen to form nitric oxide, NO. $$ce{N2(g) + O2(g) <=>[2000 K] 2NO(g)}$$
Uses
- Manufacture of ammonia
- manufacture of industrial chemicals containing nitrogen like calcium cyanamide
- providing inert atmosphere (as in iron and steel industry)
- as inert diluent for reactive chemicals
- Liquid nitrogen as a refrigerant to preserve biological materials, food items
- used in cryosurgery
() (ce{})
