
Bicarbonate is an anion (a negatively-charged ion). Its chemical formula is HCO−3. A sample compound is sodium bicarbonate.
Bicarbonate is amphoteric: it is both an acid and a base. As an acid, it reacts with bases to make carbonate, and as a base, it reacts with acids to make carbonic acid, which usually disporportionates to water and carbon dioxide.
When heated, it will react with itself as both acid and base: 2 NaHCO3 → Na2CO3 + H2O + CO2