When bicarbonate (HCO3-) and hydroxide (OH-) ions are mixed together, they can react to form water (H2O), carbon dioxide (CO2), and a small amount of carbonate (CO32-) ion:
HCO3- + OH- → H2O + CO32-
This reaction is an example of an acid-base reaction, where the bicarbonate ion acts as a weak acid and the hydroxide ion acts as a strong base. The reaction can be thought of as a neutralization reaction, where the acidic and basic species react to form a neutral product (water) and a salt (carbonate ion). The release of carbon dioxide gas is often observed in this reaction, which can cause bubbling or effervescence.