# Question #eb6b2

Apr 26, 2015

Carbon Dioxide ($C {O}_{2}$) is a gas consisting of a single kind of molecule, which makes it a pure substance. A Carbon dioxide molecule is made from one atom of Carbon and two atoms of Oxygen and this compound under normal conditions exists as a gas.

Normal air or "atmosphereric air" is a mixture of gases, including Carbon Dioxide, that is retained on earth by the planet's gravity and it's essential for life. It contains 78% nitrogen, 21% oxygen, 0.9% argon, 0.04% carbon dioxide, and small amounts of other gases including helium,argon etc.
Hence it is observed that the air around us also contains Carbon Dioxide and that Carbon Dioxide gas is a subset of the larger gaseous mixture we call Air.