Carbon dioxide


Carbon dioxide (chemical formula CO2) is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earths atmosphere in this state, as a trace gas at a concentration of 0.039 per cent by volume. However, photosynthesis cannot occur in darkness and at night some carbon dioxide is produced by plants during respiration. Carbon dioxide is produced by combustion of coal or hydrocarbons, the fermentation of sugars in beer and winemaking, by animal respiration of all animals. It is exhaled in the breath of humans and land animals. It is emitted from volcanoes, hot springs, geysers and other places where the earth’s crust is thin and is freed from carbonate rocks by dissolution. CO2 is also found in lakes at depth under the sea, and commingled with oil and gas deposits. The environmental effects of carbon dioxide are of significant interest. Carbon dioxide is an important greenhouse gas, warming the Earths surface to a higher temperature by reducing outward radiation. Atmospheric carbon dioxide is the primary source of carbon in life on Earth and its concentration in Earths pre-industrial atmosphere since late in the Precambrian eon has been regulated by photosynthetic organisms. Because human activities since the industrial revolution have rapidly increased concentrations of atmospheric carbon dioxide, it plays a major role in global warming and anthropogenic climate change. It is also a major source of ocean acidification since it dissolves in water to form carbonic acid, which is a weak acid as its ionization in water is incomplete. : CO2 + H2O H2CO3 Dry ice, sometimes referred to as "Cardice" or as "card ice" (chiefly British English), is the solid form of carbon dioxide. It is used primarily as a cooling agent. Its advantages include lower temperature than that of water ice and not leaving any residue (other than incidental frost from moisture in the atmosphere). It is useful for preserving frozen foods, ice cream, etc., where mechanical cooling is unavailable. Dry ice sublimates at −78.5 °C (−109.3 °F) at atmospheric pressure. This extreme cold makes the solid dangerous to handle without protection due to burns caused by freezing (frostbite). While generally not very toxic, the outgassing from it can cause hypercapnia due to buildup in confined locations.


Substance data page for Carbon dioxide


Chemistry educational resource for Carbon dioxide (standard InChIKey CURLTUGMZLYLDI-UHFFFAOYSA-N). Methanedione (IUPAC Name); Di-carbon oxide; carbonyl oxide; dioxidocarbon; dioxomethane; Dry ice; Dioxo-methane. Follow the page link to go to the compound page on the Learn Chemistry wiki.