Question

how to do preparation of HNO3....?

Answer 1

The Ostwald process converts ammonia to nitric acid and involves two steps. In step 1, ammonia is oxidized to form nitric oxide and also nitrogen dioxide. Then in step 2, the nitrogen dioxide that was formed is absorbed in water. This in-turn forms nitric acid.

Answer 2

Nitric acid is made by reaction of nitrogen dioxide (NO2) with water.

3 NO2 + H2O → 2 HNO3 + NO

Normally, the nitric oxide produced by the reaction is reoxidized by the oxygen in air to produce additional nitrogen dioxide.

Bubbling nitrogen dioxide through hydrogen peroxide can help to improve acid yield.

2 NO2 + H2O2 → 2 HNO3

Commercial grade nitric acid solutions are usually between 52% and 68% nitric acid. Production of nitric acid is via the Ostwald process, named after German chemist Wilhelm Ostwald. In this process, anhydrous ammonia is oxidized to nitric oxide, in the presence of platinum or rhodium gauze catalyst at a high temperature of about 500 K and a pressure of 9 bar.

4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g) (ΔH = −905.2 kJ)

Nitric oxide is then reacted with oxygen in air to form nitrogen dioxide.

2 NO (g) + O2 (g) → 2 NO2 (g) (ΔH = −114 kJ/mol)

This is subsequently absorbed in water to form nitric acid and nitric oxide.

3 NO2 (g) + H2O (l) → 2 HNO3 (aq) + NO (g) (ΔH = −117 kJ/mol)

The nitric oxide is cycled back for reoxidation. Alternatively, if the last step is carried out in air:

4 NO2 (g) + O2 (g) + 2 H2O (l) → 4 HNO3(aq)