H2CO3, formed from H2O and CO2.
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carbonic acid n a weak dibasic acid H2CO3 known only in solution that reacts with bases to form carbonates
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car·bon·ic ac·id (kahr-bonґik) the chemical species H2CO3, which exists in chemical equilibrium with dissolved carbon dioxide in water; its dissociated forms are the bicarbonate (HCO3−) and carbonate (CO32−) ions. In the blood the predominant species are HCO3 and dissolved CO2 in approximately a 20:1 ratio. The conversion of CO2 to H2CO3 is catalyzed by the enzyme carbonate dehydratase.Medical dictionary. 2011.