CO32HCO3

CO32HCO3 is not a discrete molecule but a shorthand reference to the carbonate–bicarbonate component of the aqueous inorganic carbon system. In water, dissolved carbon dioxide and its hydration product carbonic acid interconvert with bicarbonate (HCO3−) and carbonate (CO3^2−) ions through acid–base equilibria: CO2(aq) + H2O ↔ H2CO3 ↔ H+ + HCO3− ↔ H+ + CO3^2−. The relative abundances of HCO3− and CO3^2− depend largely on pH, with pKa1 around 6.3 and pKa2 around 10.3 under typical conditions.

This carbonate system acts as a major pH buffer in natural waters, soils, and the oceans. At moderate pH (roughly 6–10), bicarbonate is the dominant species, while carbonate becomes more significant at higher pH. The balance between these species influences the saturation state of carbonate minerals such as calcite and aragonite, affecting processes from rock weathering to marine carbonate precipitation and dissolution. In sea water, the carbonate system helps regulate pH and overall alkalinity, which are central to ocean chemistry and carbon cycling.

In biological contexts, bicarbonate is a key component of buffering in blood and tissues. Carbon dioxide produced by metabolism is transported in the blood largely as bicarbonate after enzymatic conversion by carbonic anhydrase, linking respiration, acid–base balance, and transport of inorganic carbon.

Analytical and environmental applications treat CO32HCO3 as the sum of carbonate and bicarbonate species. Its behavior is described by total inorganic carbon, alkalinity, and pH, which are used to model carbon cycling in water treatment, aquaria, soils, and oceans.