Carbon dioxide in Earth's atmosphere Carbon dioxide in Earth's atmosphere Carbon dioxide () is an important trace gas in Earth's atmosphere. It is an integral part of the carbon cycle, a biogeochemical cycle in which carbon is exchanged between the Earth's oceans, soil, rocks and the biosphere. Plants and other photoautotrophs use solar energy to produce carbohydrate from atmospheric carbon dioxide and water by photosynthesis. Almost all other organisms depend on carbohydrate derived from photosynthesis as their primary source of energy and carbon compounds. absorbs and emits infrared radiation at wavelengths of 4.26 µm (asymmetric stretching vibrational mode) and 14.99 µm (bending vibrational mode) and
Carbon dioxide stretching mode at 1388 cm which is only observed in the Raman spectrum. Carbon dioxide is soluble in water, in which it reversibly forms (carbonic acid), which is a weak acid since its ionization in water is incomplete. The hydration equilibrium constant of carbonic acid is formula_1 (at 25 °C). Hence, the majority of the carbon dioxide is not converted into carbonic acid, but remains as molecules, not affecting the pH. The relative concentrations of , and the deprotonated forms (bicarbonate) and (carbonate) depend on the pH. As shown in a Bjerrum plot, in neutral or slightly alkaline water (pH