Calcium Carbonate - Chemistry

Chemistry

Calcium carbonate shares the typical properties of other carbonates. Notably:

• it reacts with strong acids, releasing carbon dioxide:

CaCO_3(s) + 2 HCl_(aq) → CaCl_2(aq) + CO_2(g) + H₂O_(l)

• it releases carbon dioxide on heating, called a thermal decomposition reaction, (to above 840 °C in the case of CaCO₃), to form calcium oxide, commonly called quicklime, with reaction enthalpy 178 kJ / mole:

CaCO_3(s) → CaO_(s) + CO_2(g)

Calcium carbonate will react with water that is saturated with carbon dioxide to form the soluble calcium bicarbonate.

CaCO₃ + CO₂ + H₂O → Ca(HCO₃)₂

This reaction is important in the erosion of carbonate rocks, forming caverns, and leads to hard water in many regions.

An unusual form for calcium carbonate is ikait with crystal water, CaCO₃ - 6 H₂O. Ikait is only stable below 6 centigrades.