2NO2 -- (catalyst) --> N2 + 2O2
Used in car exhaust pipe to remove harmful gases.
2NO + O2 -- (cooling) --> 2NO2
2NO2 + H2O --> HNO2 + HNO3
acid rain formation
During lightning,or in a hot car engine,nitrogen and oxygen in air will combine:
N2 + 2O2 --> 2NO2