carbonate system

The carbonate system is an interacting set of chemical reactions and their characteristics that determine the equilibrium of the chemistry (chemical equilibrium) resulting from water and carbon dioxide (CO₂) in each others' presence at specific temperatures and pressures.

Water and carbon dioxide react to each other to create carbonic acid (H₂CO₃) which dissociates into a hydrogen ion and bicarbonate (HCO₃), which in turn, dissociates into a hydrogen ion and carbonate (CO₃). The reverse of each of these dissociations also occurs, but the likelihoods of the opposing reactions are not identical, each reaction's likelihood depending upon conditions that include temperature and pressure. If conditions are stable, abundances evolve until the resulting reactions are in balance. This determines the acidity of such water, which includes any water in the presence of the Earth's atmosphere such as oceans, lakes, etc.