1. Ostwald Process:
This is the most common industrial method for producing nitric acid. It involves the following steps:
* Oxidation of ammonia: Ammonia (NH3) is oxidized with air in the presence of a platinum catalyst at high temperature (850-900 °C) to form nitric oxide (NO).
* 4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g)
* Further oxidation: The nitric oxide (NO) is further oxidized with air to form nitrogen dioxide (NO2).
* 2 NO (g) + O2 (g) → 2 NO2 (g)
* Absorption: Nitrogen dioxide (NO2) is absorbed in water to form nitric acid (HNO3) and nitric oxide (NO).
* 3 NO2 (g) + H2O (l) → 2 HNO3 (aq) + NO (g)
* Recycling: The nitric oxide (NO) is recycled back to the second step for further oxidation.
2. Other methods:
* Direct reaction of nitrogen dioxide with water: This method is less efficient than the Ostwald process.
* 3 NO2 (g) + H2O (l) → 2 HNO3 (aq) + NO (g)
* Reaction of nitrogen oxides with hydrogen peroxide: This method is used to produce high-purity nitric acid.
* NO2 (g) + H2O2 (l) → HNO3 (aq) + H2O (l)
* Laboratory synthesis: Nitric acid can be synthesized in the laboratory by reacting concentrated sulfuric acid with a nitrate salt, such as sodium nitrate.
* NaNO3 (s) + H2SO4 (l) → NaHSO4 (s) + HNO3 (g)
Regardless of the method used, the formation of nitric acid always involves the oxidation of nitrogen and the presence of water.
