Is air a mixture or a compound

Composition of the air

Air is a gas mixture surrounding the earth's atmosphere, which when dry is made up of the main components nitrogen
(78.08% by volume) and oxygen (20.95% by volume). There are also noble gases (such as argon, helium, krypton and xenon) and other trace substances (such as carbon dioxide, methane, hydrogen, nitrous oxide and carbon monoxide), the total of which is less than 1% by volume.

In addition to the gases mentioned, the air also contains:

  • Water vapor, the content of which in the atmosphere fluctuates over time and regionally and averages 0.4%
  • Dust particles
  • Aerosols (small solid and liquid particles suspended in the air)
  • Sulfur and nitrogen compounds
  • volatile organic compounds (VOC)
  • Ozone (secondary product, regional and temporal differences)
  • radicals generated in the atmosphere

The proportions of naturally occurring gases change only slightly and, with the exception of water vapor and ozone, are largely evenly distributed up to a height of approx. 100 km (homosphere) due to the good mixing of the atmosphere. However, fluctuations in the individual components (in particular the trace gases) can occur from time to time and in certain areas, caused by volcanic eruptions or putrefaction processes, for example.

In addition to the natural constituents of the air, human (anthropogenic) air admixtures (e.g. nitrogen oxides, carbon monoxide, sulfur dioxide) can lead to long-term changes in the corresponding proportions. The long-lived trace substances that count among the greenhouse gases, such as B. methane and carbon dioxide can also have climate-relevant effects.