What does no2 polar

Structural formula
Surname Nitrogen dioxide
other names
  • Nitrogen dioxide
  • Nitrogen (IV) oxide
Molecular formula NO2
CAS number 10102-44-0
Brief description red-brown, pungent chlorine-like odor and easily liquefiable gas
Molar mass 46.01 g mol−1
Physical state gaseous
density 3.663 g / l (gas density at 0 ° C)[1]
Melting point −11.2 ° C[1]
boiling point 21.2 ° C[1]
Vapor pressure

0.963 bar[1] (20 ° C)


easily soluble in water

safety instructions

no MAK, as carcinogenic[1]

As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions.

Nitrogen dioxide, NO2, is a red-brown, pungent chlorine-like smelling gas that can be easily liquefied and occurs as a trace gas in the atmosphere with the highest values ​​near the ground.


The critical temperature for NO2 is 157.8 ° C and the critical pressure is 10 MPa.

NO decomposes above 200 ° C2 in O2 and NO, in addition it is relatively soluble in water, strongly oxidizing and has a pungent odor. The red-brown paramagnetic NO2 has a strong oxidizing effect and is associated with the diamagnetic, colorless dinitrogen tetroxide N.2O4 in equilibrium, whereby this equilibrium shifts to the left with increasing temperature:

N2O4 and NO2 behave like a mixed anhydride of nitric acid and nitrous acid. With alkali hydroxide solutions they form nitrates and nitrites, e.g. B:

When introducing NO2 in water there is disproportionation to nitric acid and nitrous acid, the latter in the acidic solution to NO2, NO and water disintegrates.

In the presence of air, NO becomes NO2 oxidized, so that ultimately all of the NO2 is converted into nitric acid:


In terms of laboratory technology, NO2 by heating heavy metal nitrates. Technically, it is obtained as an intermediate product in the synthesis of nitric acid by the air oxidation of NO. It is also formed when nitric acid reacts with copper, since this acid reaction does not take place with the formation of hydrogen.


Nitric dioxide is used to produce nitric acid, for which it is introduced into water and reacts with it. Its dimer nitrogen tetroxide is used in rocket science as an oxidizing agent.

safety instructions

Nitrogen dioxide is highly toxic and is hardly noticed in low concentrations. Inhaled nitrogen dioxide causes headaches and dizziness. Higher concentrations can cause shortness of breath and pulmonary edema.

See also


  1. abcde BGIA_Gestis hazardous substance database

Categories: Toxic Substance | Nitrogen compound | Oxygen connection