Calcium Carbonate , CaCO3
Calcium carbonate is also called limestone. It occurs in nature as Chalk, marbles, corals, calcite. Mixed with magnesium carbonate it occurs as dolomite.
Preparation of Calcium Carbonate
1) From slaked lime
It can be prepared by passing a calculated quantity of CO2 through slaked lime.
Ca(OH)2+ CO2 ——> CaCO3 ↓ + H2O
2) From calcium chloride
It is prepared by adding an aqueous solution of sodium carbonate to calcium chloride.
CaCl2 + Na2CO3 ——-> CaCO3 ↓ + 2 NaCl
Properties of Calcium Carbonate
1) It is a white solid almost insoluble in water.
2) When heated to 1070-1270 K, it decomposes to evolve CO2.
CaCO3 ——-> CaO + CO2
3) It reacts with dilute acids liberating CO2.
Uses of Calcium Carbonate
1) Calcium carbonate along with magnesium carbonate is used as a flux in the extraction of metals such as iron.
2) Precipitated calcium carbonate is extensively used in the manufacture of high quality paper.
3) It is also used as an antacid ,mild abrasive in toothpaste ,a constituent of chewing gum and a filler in cosmetics.
4) It is used as a raw material for the manufacture of sodium carbonate in solvay -Ammonia process.
5) It is used as a building material in form of marble and manufacture of quicklime.