Nitrogen Dioxide - Preparation and Reactions

Preparation and Reactions

Nitrogen dioxide typically arises via the oxidation of nitric oxide by oxygen in air:

2 NO + O2 → 2 NO2

In the laboratory, NO2 can be prepared in a two step procedure by thermal decomposition of dinitrogen pentoxide, which is obtained by dehydration of nitric acid:

2 HNO3 → N2O5 + H2O
2 N2O5 → 4 NO2 + O2

The thermal decomposition of some metal nitrates also affords NO2:

2 Pb(NO3)2 → 2 PbO + 4 NO2 + O2

Alternatively, reduction of concentrated nitric acid by metal (such as copper).

4 HNO3 + Cu → Cu(NO3)2 + 2 NO2 +2 H2O

Or finally by adding concentrated nitric acid over tin. Stannic acid is produced as byproduct.

4HNO3 + Sn → H2O + H2SnO3 + 4 NO2

Read more about this topic:  Nitrogen Dioxide

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