After studying this Power Points Presentation, you will be able to- Learning Objectives: Learn about the ammonia and its properties.

Ammonia is present in small quantities in air and soil where it is formed by the decay of nitrogenous organic matter e.g., urea. Preparation NH 2 CONH 2 + 2H 2 O → (NH 4 ) 2 CO 3 NH 3 + H 2 O + CO 2 On a small scale ammonia is obtained from ammonium salts which decompose when treated with caustic soda or lime. 2NH 4 Cl + Ca(OH) 2 → 2NH 3 + 2H 2 O + CaCl 2 (NH 4 ) 2 SO 4 + 2NaOH → 2NH 3 + 2H 2 O + Na 2 SO 4 On a large scale, ammonia is manufactured by Haber’s process. N 2 (g) + 3H 2 (g) 2NH 3 (g); Δf H 0 = – 46.1 kJ mol –1

In accordance with Le Chatelier’s principle, high pressure would favour the formation of ammonia. The optimum conditions for the production of ammonia are a pressure of 200 × 10 5 Pa (about 200 atm), a temperature of ~ 700 K and the use of a catalyst such as iron oxide with small amounts of K 2 O and Al 2 O 3 to increase the rate of attainment of equilibrium

The flow chart for the production of ammonia.

Properties Physical Properties:  Ammonia is a colourless gas with a pungent odour. Its freezing and boiling points are and K respectively.  In the solid and liquid states, it is associated through hydrogen bonds as in the case of water and that accounts for its higher melting and boiling points than expected on the basis of its molecular mass.  The ammonia molecule is trigonal pyramidal with the nitrogen atom at the apex. It has three bond pairs and one lone pair of electrons as shown in the structure.

Chemical Properties It forms ammonium salts with acids, e.g., NH 4 Cl, (NH 4 ) 2 SO 4 etc. As a weak base, it precipitates the hydroxides of many metals from their salt solutions. 6 2FeCl 3 (aq) + NH 4 OH(aq) → Fe 2 O 3.xH 2 O(s) + 3NH 4 Cl(aq) (brown ppt) ZnSO 4 + 2NH 4 OH → Zn(OH) 2 + (NH 4 ) 2 SO 4 White ppt.

Complex formation Ammonia is a Lewis base. It donates the electron pair to metal ions and the form complex. 7 For example: Cu 2+( aq) + 4NH 3 (aq) [Cu(NH 3 ) 4 ] 2+ (aq) Blue Deep blue Ag +( aq) + Cl¯(aq) → AgCl AgCl(s) + 4NH 3 (aq) → [Ag(NH 3 ) 4 ] 2+ (aq) White ppt Soluble

Uses Ammonia is used : In produce of various nitrogenous fertilisers (ammonium nitrate, urea, ammonium phosphate and ammonium sulphate) in the manufacture of some inorganic nitrogen compounds, the most important one being nitric acid. Liquid ammonia is also used as a refrigerant. 8