Nitrogen dioxide (NO2) is a reddish-brown, toxic gas composed of nitrogen and oxygen. It's a major air pollutant, primarily emitted from combustion processes, and contributes to respiratory and environmental problems. NO2 is used as a fuel in rockets besides being used to prepare HNO3
Laboratory Preparation of Nitrogen Dioxide
In the laboratory NO2 is prepared by thermal decomposition of Pb(NO3)2. Thus:
2Pb(NO3)2→ 2PbO + 4NO2 + O2
Please Note: Hydrated nitrate salts on heating react violently and explode.
Physical Properties of Nitrogen Dioxide
NO2 is a poisonous gas, main source being the exhaust of auto mobiles.
At room temperature it is a deep brown gas.
It does not support combustion.
It is not combustible
Chemical Properties of Nitrogen Dioxide
1) With cold water NO2 reacts to give a mixture of HNO2 and HNO3 acid.
2NO2 + H2O → HNO2 + HNO3
2) With hot water the reaction is
3NO2 + H2O → 2HNO3 + NO
3) Being acidic it reacts with bases as
2NO2 + 2KOH → KNO3 + H2O + KNO2
4) It is also a strong oxidising agent.
H2S + 3NO2→ 3NO + H20 + S02
5) With excess oxygen and water NO2 gives HNO3.
4NO2 + O2 + 2H2O → 4HNO3
6) It reacts with concentrated H2SO4 to give nitrosyl hydrogen sulphate
