Explain the commercial method of preparation of nitric acid. (or) How nitric acid is prepared by Ostwald's process.

Explanation

Commercial method of preparation
(i) Nitric acid prepared in large scales using Ostwald's process. In this method ammonia from Haber's process is mixed about 10 times of air.
(ii) This mixture is preheated and passed into the catalyst chamber where they come in contact with platinum gauze.
(iii) The temperature rises to about 1275 K and the metallic gauze brings about the rapid catalytic oxidation of ammonia resulting in the formation of NO, which then oxidised to nitrogen dioxide.
`4NH_(3)+5O_(2)rarr 4NO+6H_(2)O+120kJ`
`2NO+O_(2) rarr 2NO_(2)`
(iv) The nitrogen dioxide produced is passed through a series of adsorption towers. It reacts with water to give nitric acid. Nitric acid formed is bleached by blowing air.
`6NO_(2)+3H_(2)O rarr 4HNO_(3)+2NO+H_(2)O`