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Aqueous carbon dioxide reacts with water to form carbonic acid which is very unstable and will dissociate rapidly into hydronium and bicarbonate. Therefore, in seawater, dissolved inorganic carbon is commonly referred to as the collection of bicarbonate, carbonate ions, and dissolved carbon dioxide (CO 2, H 2 CO 3, HCO − 3, CO 2− 3).
CO2SYS is a family of software programs that calculate chemical equilibria for aquatic inorganic carbon species and parameters. Their core function is to use any two of the four central inorganic carbon system parameters (pH, alkalinity, dissolved inorganic carbon, and partial pressure of carbon dioxide) to calculate various chemical properties of the system.
The aquatic inorganic carbon system is composed of the various ionic, dissolved, solid, and/or gaseous forms of carbon dioxide in water. These species include dissolved carbon dioxide, carbonic acid, bicarbonate anion, carbonate anion, calcium carbonate, magnesium carbonate, and others. The relative amounts of each species in a body of water ...
In even a slight presence of water, carbonic acid dehydrates to carbon dioxide and water, which then catalyzes further decomposition. [6] For this reason, carbon dioxide can be considered the carbonic acid anhydride. The hydration equilibrium constant at 25 °C is [H 2 CO 3]/[CO 2] ≈ 1.7×10 −3 in pure water [12] and ≈ 1.2×10 −3 in ...
It constitutes around 38,000 Pg C [18] and includes dissolved carbon dioxide (CO 2), bicarbonate (HCO − 3), carbonate (CO 2− 3), and carbonic acid (H 2 C O 3). The equilibrium between carbonic acid and carbonate determines the pH of the seawater. Carbon dioxide dissolves easily in water and its solubility is inversely related to temperature.
The following chart shows the solubility of various ionic compounds in water at 1 atm pressure and room temperature (approx. 25 °C, 298.15 K). "Soluble" means the ionic compound doesn't precipitate, while "slightly soluble" and "insoluble" mean that a solid will precipitate; "slightly soluble" compounds like calcium sulfate may require heat to precipitate.
‡ Second column of table indicates solubility at each given temperature in volume of CO 2 as it would be measured at 101.3 kPa and 0 °C per volume of water. The solubility is given for "pure water", i.e., water which contain only CO 2. This water is going to be acidic. For example, at 25 °C the pH of 3.9 is expected (see carbonic acid).
The exact value of the CCD depends on the solubility of calcium carbonate which is determined by temperature, pressure and the chemical composition of the water – in particular the amount of dissolved CO 2 in the water. Calcium carbonate is more soluble at lower temperatures and at higher pressures.