The Chemistry of Limestone Formation
Gaseous CO2 is in equilibrium with aqueous CO2 in natural waters:
CO2 (g) CO2 (aq)
H2O(l)
The concentration of CO2 is proportional to the partial pressure
of CO2 (g) in contact with the water (Henryís Law; section 13.3):
[CO2 (aq)] (proportional to) PCO2
The reaction of CO2 with water produces H3O+:
CO2 (aq) + 2 H2O(l) H3O+(aq) + HCO3-(aq)
Thus, the presence of CO2 (aq) forms H3O+, which increases the
solubility of CaCO3:
CaCO3 (s) + CO2 (aq) + H2O(l) Ca2+(aq) + 2 HCO3-(aq)
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