Give preparation of ammonia.

Explanation

Ammonia is present in small quantities in air and soil where it is formed by the decay of nitrogenous organic matter e.g. urea.
`H_(2)N -underset(O)underset(||)C - NH_(2) + 2H_(2)O to (NH_(4))_(2)CO_(2) On a small scale ammonia is obtained from ammonium salts which decompose when treated with caustic soda or calcium hydroxide.
`2NH_(4)Cl + Ca(OH)_(2) to 2NH_(3) +2H_(2)O + CaCl_(2)`
`(NH_(4))_(2)SO_(4) + 2NaOH to 2NH_(3) + 2H_(2)O + Na_(2)SO_(4)`
On large scale, ammonia is manufactured by Haber.s process
`N_(2)(g) + 3H_(2)(g) 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 xx 10^5` Pa (200 bar), a temperature of - 700 K and use of catalyst such as iron oxide with small amounts of `K_20` and `Al_2O_(3)` to increase the rate of attainment of equilibrium earlier molybdenum was used as promoter.