Carbonate-containing salts are industrially and mineralogically ubiquitous. The term "carbonate" is also commonly used to refer to one of these salts or carbonate minerals. Most common is calcite, or calcium carbonate, CaCO3, the chief constituent of limestone. The process of removing carbon dioxide from these salts by heating is called calcination.
The term is also used as a verb, to describe the process of raising carbonate and bicarbonate concentrations in soda, see also carbonated water, either by the introduction under pressure of carbon dioxide gas into the bottle, or by dissolving carbonate or bicarbonate salts into the water.
The structure and bonding of the carbonate ion cannot be properly represented by its Lewis structure, which depicts CO32− with two long single bonds and one short double bond:
Resonance structures can be used to depict the carbonate ion:
In reality, CO32− has three equally long C-O bonds:
In aqueous solution, carbonate, bicarbonate, carbon dioxide, and carbonic acid exist together in a dynamic equilibrium. In strongly basic conditions, the carbonate ion predominates, while in weakly basic conditions, the bicarbonate ion is prevalent. In more acid conditions, aqueous carbon dioxide, CO2(aq), is the main form, which, with water, H2O, is in equilibrium with carbonic acid - the equilibrium lies strongly towards carbon dioxide. Thus sodium carbonate is basic, sodium bicarbonate is weakly basic, while carbon dioxide itself is a weak acid.
Carbonated water is formed by dissolving CO2 in water under pressure. When the partial pressure of CO2 is reduced, for example when a can of soda is opened, the equilibrium for each of the forms of carbonate (carbonate, bicarbonate, carbon dioxide, and carbonic acid) shifts until the concentration of CO2 in the solution is equal to the solubility of CO2 at that temperature and pressure. In living systems an enzyme, carbonic anhydrase, speeds the interconversion of CO2 and carbonic acid.
When pH is too high, the concentration of hydrogen ions in the blood is too low, so the kidneys excrete bicarbonate (HCO3−). This causes the equation to shift right, essentially increasing the concentration of hydrogen ions, causing a more acidic pH.
Significant carbonate deposits have not been found on Mars via remote sensing or in situ missions, even though Martian meteorites contain small amounts and groundwater may have existed at both Gusev and Meridiani Planum.
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US Patent Issued to University of South Florida on Sept. 6 for "Sensor for Direct Measurement of Carbonate Ions in Seawater" (Florida Inventor)
Sep 12, 2011; ALEXANDRIA, Va., Sept. 12 -- United States Patent no. 8,012,760, issued on Sept. 6, was assigned to University of South Florida...
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May 09, 2013; ALEXANDRIA, Va., May 9 -- United States Patent no. 8,435,910, issued on May 7, was assigned to National Institute for Materials...