Nitrogen dioxide is a kind of nitrogen oxide, which can be produced by human activities and natural behavior. Lightning and microbial life activities are the main natural sources of nitrogen dioxide. In addition to the natural source of nitrogen dioxide, the nitrogen dioxide that can cause environmental pollution mainly comes from the combustion of fuel, and the exhaust gas of urban vehicles also contains more nitrogen dioxide. In addition, some nitrogen dioxide can be produced by industrial processes. It is estimated that about 53 million tons of nitrogen oxides are emitted each year by man-made sources worldwide. A map of the global distribution of NO2, produced by Germany in 2004 using satellite data, shows that global NO2 levels are high in most parts of Europe, some cities in North America and parts of the North-East of China. Nitrogen dioxide can cause a wide range of environmental problems. It is one of the main factors of forming photochemical smog, and also one of the sources of acid rain. Nitrogen dioxide is inhaled by the human body, can produce strong stimulation and corrosion of lung tissue, thus causing pulmonary edema. People with respiratory conditions, such as asthma, are more susceptible to NO2. In children, nitrogen dioxide can cause dysplasia of the lungs. Studies have shown that long-term exposure to human nitrogen dioxide can cause structural changes in the lungs.

Lightning is a natural source of nitrogen dioxide

Industrial use of oxygen in the air to oxidize nitric oxide to produce nitrogen dioxide:

2 no + O2 ─ no2 - > 2

In the laboratory, it can be prepared by oxidation of nitric oxide NO or by the action of concentrated nitric acid with copper chips, or by the decomposition of lead nitrate by heating:

Pb (NO3) 2 ─ 2-4 no2 + 2 pbo + O2 write

NO2 can also be prepared by thermal decomposition of nitrogen pentoxide. Nitrous oxide can be obtained by dehydration with nitric acid.

2HNO3=N2O5+H2O

2 n2o5 = 4 no2 + O2 write

The resulting gas is condensed to remove nitric acid, and then dried by phosphorus pentoxide, resulting in a relatively pure nitrogen dioxide. Nitrogen dioxide can also be produced by co-heating copper with concentrated nitric acid:

Cu+4HNO3=Cu (NO3) 2+2NO2↑+H2O