In inorganic chemistry, bicarbonate (IUPAC-recommended nomenclature: hydrogen carbonate) is an intermediate form in the deprotonation of carbonic acid. Its chemical formula is HCO3−.
Bicarbonate serves a crucial biochemical role in the physiological pH buffering system.
The bicarbonate ion (hydrogen carbonate ion) is an anion with the empirical formula HCO3− and a molecular mass of 61.01 daltons; it consists of one central carbon atom surrounded by three oxygen atoms in a trigonal planar arrangement, with a hydrogen atom attached to one of the oxygens. It is isoelectronic with nitric acid. The bicarbonate ion carries a negative one formal charge and is the conjugate base of carbonic acid, H2CO3; it is the conjugate acid of CO32−, the carbonate ion as shown by these equilibrium reactions.
CO32− +2 H2O ↔ HCO3− + H2O + OH− ↔ H2CO3 +2 OH−
H2CO3 +2 H2O ↔ HCO3− + H3O+ + H2O ↔ CO32− +2 H3O+
A bicarbonate salt forms when a positively charged ion attaches to the negatively charged oxygen atoms of the ion, forming an ionic compound. Many bicarbonates are soluble in water at standard temperature and pressure, in particular sodium bicarbonate and magnesium bicarbonate; both of these substances contribute to total dissolved solids, a common parameter for assessing water quality.
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