Bicarbonate
anion
In inorganic chemistry, bicarbonate (American English: ; IUPAC-recommended nomenclature: hydrogencarbonate) is an intermediate form in the deprotonation of carbonic acid. It is a polyatomic anion with the chemical formula HCO3–.
Bicarbonate serves a crucial biochemical role in the physiological pH buffering system.
The term "bicarbonate" was coined in 1814 by the English chemist William Hyde Wollaston. In his original use the bi- referred to the presence of two carbonic acid derivatives in carbonates made by reaction with a base. Despite its modern use in reference to a molecule with only one carbon atom it lives on as a trivial name.
Chemical properties
The bicarbonate ion (hydrogencarbonate 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 (HNO3). The bicarbonate ion carries a negative one formal charge and is an amphiprotic species which has both acidic and basic properties. It is both the conjugate base of carbonic acid (H2CO3); and 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.
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