Reactions releasing nitrogen oxides into the atmosphere:

» Nitric oxide can be produced at very high temperatures – lightning, internal combustion engines which produce nitrogen monoxide, nitric oxide or nitrogen(II) oxide with temperatures above 1300oC

N2 + O2 →2NO


» Nitric oxide can be formed with slow reaction with further oxygen to produce nitrogen dioxide.

2NO + O2 → 2NO2



» By water being the product, nitric oxide can be industrially prepared by catalytic oxidation of ammonia.

4 NH3 + 5 O2 → 4 NO + 6 H2O



» Nitric oxide can be prepared in the laboratory by the reaction of concentrated nitric acid on copper.

3Cu+ 8HNO3→ 3Cu(NO3) 2 + 2NO +4H2O



» Nitrogen dioxide forms nitric oxide and oxygen when heated.

2NO2 → 2 NO + O2


» Manufacturing production of nitric acid from ammonia. The nitric acid decomposes to nitrogen dioxide.

4 HNO3 → 4 NO2 + 2H2O + O2


» Nitrogen monoxide reacts with oxygen in the air and forms acidic nitrogen dioxide (nitrogen(IV)oxide)

2NO + O2 →2NO2