Calcium Carbonate, CaCO3

Calcium Carbonate, CaCO₃

Calcium carbonate occurs in nature in several forms like limestone, chalk, marble etc. it can be prepared by passing carbon dioxide through slaked lime or by the addition of sodium carbonate to calcium chloride.

Ca(OH)₂   +   CO₂    →    CaCO₃   +   H₂O

CaCl₂   +   Na₂CO₃   →    CaCO₃   +   2NaCl

Excess of carbon dioxide should be avoided since this leads to the formation of water soluble calcium hydrogencarbonate.

Calcium carbonate is a white fluffy powder. It is almost insoluble in water. When heated to 1200 K, it decomposes to evolve carbon dioxide.

It reacts with dilute acid to liberate carbon dioxide.

CaCO₃   +   2HCl    →   CaCl₂   +   H₂O   +   CO₂

CaCO₃   +   H₂SO₄    →    CaSO₄   +   H₂O   +   CO₂

Uses

It is used as a building material in the form of marble and in the manufacture of quick lime. Calcium carbonate along with magnesium carbonate is used as a flux in the extraction of metals such as iron. Specially precipitated CaCO₃ is extensively used in the manufacture of high quality paper. It is also used as an antacid, mild abrasive in tooth paste, a constituent of chewing gum, and filler in cosmetics