Carbon dioxide dissolves in water to form carbonic acid. CO2+H2O⇌H2CO3 Carbonic acid is a weak acid. It dissociates to form carbonate and bicarbonate ions. H2CO3+H2O⇌HCO3−+H3O+ Bicarbonate ion dissociates to form carbonate ion. HCO3−+H2O⇌CO32−+H3O+ Hence, the species present in the solution are CO2,H2CO3,HCO3−,CO32−.