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What is the approximate gas composition of dry air by volume?

  • A

    Oxygen 21%
    Water vapour 78%
    Noble gases/carbon dioxide 1%

  • B

    Oxygen 21%
    Nitrogen 78%
    Noble gases / carbon dioxide 1%

  • C

    Oxygen 78%
    Water vapour 21%
    Nitrogen 1%

  • D

    Nitrogen 21%
    Oxygen 78%
    Noble gases/carbon dioxide 1%

The atmosphere is a mixture of gases, but it also contains other non-gaseous substances, such as water droplets, and particles of smoke, dust, and ash. Up to a height of about 60 km, the composition of gases in the atmosphere remains very consistent. Above 60 km, the effect of gravity alters the composition.

The approximate composition of dry air by volume is:

  • Nitrogen: 78%
  • Oxygen: 21%
  • Other gases: 1% (including Argon 0.95%, Carbon dioxide 0.05%, and trace gases).

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