Nitrogen dioxide
- Nitrogendioxid
- Nitrogen ( IV) oxide
- Nitrogen peroxide
Red-brown, pungent gas
Gaseous
- 3.66 g · l-1 (gas density at 0 ° C)
- 1.439 g · cm -3 (liquid at boiling point )
-11.2 ° C
21.2 ° C
963 hPa ( 20 ° C)
Hydrolysis in water
Risk
0.95 mg / m³ (recommended)
33.2 kJ / mol
Template: Infobox chemical / molecular formula search is not possible
Nitrogen dioxide, NO2, is a reddish brown, poisonous, pungent chlorine- like smelling gas, which can be easily liquefied under dimerization to N2O4 ( dinitrogen tetraoxide ) and occurs as a trace gas in the atmosphere with the highest values near the ground.
Nitrogen dioxide belongs to the group of nitrogen oxides.
Nitrous gases is the trivial name for a mixture of nitric oxide ( NO) and nitrogen dioxide NO2.
Properties
The critical temperature of 157.8 ° C is NO2 and the critical pressure is about 10 MPa.
Above 200 ° C decomposes into NO2 O2 and NO, in addition, it is relatively soluble in water and has a pungent, irritating odor cough. The red-brown paramagnetic NO2 has a strong oxidizing and reducing and communicating with the diamagnetic colorless dinitrogen tetroxide N2O4 in equilibrium, this equilibrium shifts to the left with increasing temperature and dimerizes below 0 ° C to completely colorless dinitrogen tetroxide:
At the same time the color changes upon cooling of the gas from reddish brown color on pale yellow. By this equilibrium, the density changes. This is at 0 ° C for an ideal pure NO2 gas, 2.05 g / l and for the ideal gas N2O4 4.1 g / l The real value of 3.6 g / l thus applies to an equilibrium mixture of the two gases. The critical point is 157.8 ° C, 101.32 in cash and 0.557 kg / l; the triple point at -11.20 ° C and 0.1864 bar.
N2O4 and NO2 behave like the mixed anhydride of nitric acid and nitrous acid. With alkali metal hydroxide to form nitrates and nitrites, eg:
With the introduction of NO2 in water it is disproportionation to give nitric acid and nitrous acid, the latter being divided into the acidic solution to NO2, NO and water.
In the presence of air, NO is oxidized into NO2, so that ultimately the entire introduced NO2 is converted to nitric acid:
Production
The laboratory can NO2 are prepared by heating of heavy metal nitrates. Technically, it is obtained as an intermediate in the synthesis of nitric acid by air oxidation of NO. Furthermore, it arises from the reaction of nitric acid with copper, as these acid reaction does not proceed with the formation of hydrogen. It also arises in arcs in air, for example, to Jacob ladders.
Formation by natural and industrial processes
NO2 produced by the burning of fossil fuels such as gas, coal and oil, and is thus include part of the exhaust gas of motor vehicles, oil and gas boilers and gas and coal power plants.
To a lesser extent nitrogen dioxide produced during the production of paper.
NO2 causes the brown color of the mushroom cloud in above-ground nuclear weapons tests.
Nitrogen dioxide has an influence on the atmospheric chemistry and the ozone content in the troposphere.
Acid rain is caused by the formation of nitric acid (HNO3) in the atmosphere by reaction of ( 2 NO2 H2O → HNO3 HNO2 ) or by uptake of N2O5 in aerosol particles and subsequent formation of NO3- in the liquid phase.
Thunderstorms are a natural source of atmospheric nitrogen dioxide.
Use
Nitrogen is used for the production of nitric acid, to which it is introduced into the water and reacts with it. His dimer dinitrogen tetroxide is used in rocket technology as the oxidant. It also serves as a non-aqueous solvent and is used for the preparation of addition compounds with metals (eg, copper, nickel ) and ammonium nitrate used ( in admixture with NO).
Safety
Nitrogen dioxide is highly toxic and is hardly noticed in low concentrations. Inhaled nitrogen dioxide triggers headaches and dizziness. Higher concentrations can cause shortness of breath and pulmonary edema. If inhaled nitrogen dioxide in concentrations of 40-100 ľg/m3 a long time, it comes to health problems.
Nitrogen oxides have a characteristic pungent odor and may cause a delay of more than 24 hours ( latency ) after inhaling yet to pulmonary edema. In men, impotence can also occur as a late effect in more frequent inhalation.