Calcium carbonate Formula Calcium carbonate Uses, Properties, Structure and Formula. CaO + H 2 O → Ca(OH) 2 Ca(OH) 2 + CO 2 → CaCO 3 + H 2 O Physical properties: Pure CaCO 3 is an odorless, fine white powder. It has a density of g/mL and melting point of 1,339 °C, as its calcite form.