Balanced equation for catalytic oxidation of ammonia
Answers
The equation for the catalytic oxidation of ammonia is:
4NH3 + 5O2 →4NO + 6H2O
The catalyst is a wire mesh consisting of platinum and rhodium.
But this is only a small portion of the Ostwald process for the oxidation of ammonia to produce nitric acid.The full process is as follows:
Ammonia is converted to nitric acid in two stages. It is oxidized (in a sense "burnt") by heating with oxygen in the presence of a catalyst such as platinum with 10% rhodium, to form nitric oxide and water. This step is strongly exothermic, making it a useful heat source once initiated:
4 NH3 (g) + 5 O2 (g) → 4 NO (g) + 6 H2O (g) (ΔH = −950 kJ/mol)
Stage two (combining two reaction steps) is carried out in the presence of water in an absorption apparatus. Initially nitric oxide is oxidized again to yield nitrogen dioxide:
2 NO (g) + O2 (g) → 2 NO2 (g) (ΔH = −114 kJ/mol)
This gas is then readily absorbed by the water, yielding the desired product (nitric acid, albeit in a dilute form), while reducing a portion of it back to nitric oxide:
3 NO2 (g) + H2O (l) → 2 HNO3 (aq) + NO (g) (ΔH = −117 kJ/mol)
The NO is recycled, and the acid is concentrated to the required strength by distillation.
Answer:
4NH3 + 5O2 -----> 4NO + 6H20