What is the chemical formula for bicarbonate?

Bicarbonate is a crucial species in various biological and geological processes, particularly in maintaining pH balance in water bodies and human physiology. The chemical formula for bicarbonate is represented as HCO3-. This notation indicates that it is a negatively charged ion (anion) consisting of one hydrogen atom, one carbon atom, and three oxygen atoms.

The presence of the hydrogen atom is what differentiates bicarbonate from its conjugate base, carbonate (CO3 2-), which has an additional negative charge due to the absence of that hydrogen. Bicarbonate plays an important role in buffering solutions, making it vital for the carbonate-bicarbonate system that helps regulate pH in natural waters and biological fluids.

The other options represent different chemical species with distinct functions and structures: H2CO3 is carbonic acid and a precursor to bicarbonate but is not the bicarbonate ion itself. CO3 2- represents the carbonate ion and, as mentioned, is distinct from bicarbonate. Lastly, CaCO3 is calcium carbonate, a solid compound that comprises both the carbonate ion and calcium. Thus, the correct representation of bicarbonate is HCO3-, reflecting its unique ionic form and significance in chemical equilibria.