Calcium carbonate

Categories: Incomplete inorganic compound articles | Calcium compounds | Carbonates

Calcium carbonate
Image:Calcium carbonate.jpg
General
Other names	see text
Molecular formula	CaCO₃
Molar mass	100.09 g/mol
Appearance	white solid
CAS number	[471-34-1]
Properties
Density and phase	2.8 g/cm³, solid
Solubility in water	insoluble
Melting point	825 °C decomp.
Structure
Coordination geometry	?
Crystal structure	?
Dipole moment	? D
Hazards
MSDS	External MSDS
EU classification	not listed
Supplementary data page
Structure and properties	n, ε_r, etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Related compounds
Other anions	Calcium bicarbonate
Other cations	Magnesium carbonate Strontium carbonate
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Calcium carbonate is a chemical compound, with chemical formula Ca C O₃.

It is commonly used as an antacid, and is the active ingredient in agricultural lime. It is a common substance found as rock in all parts of the world and is the main component of seashells and the shell of snails.

1 Occurance
2 Preparation
3 Chemical properties
4 Uses
5 External link

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Occurance

Calcium carbonate is found naturally as the following minerals and rocks:

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Preparation

The vast majority of calcium carbonate used in industry is extracted by mining or quarrying. When pure calcium carbonate is required (e.g. for food or pharmaceutical use), it is prepared by passing carbon dioxide into a solution of calcium hydroxide: the calcium carbonate precipitates out, and this grade of product is referred to as precipitated.

Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

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Chemical properties

See also: Carbonate

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

it reacts with strong acids, releasing carbon dioxide.

CaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂O

it releases carbon dioxide on heating (to above 825 °C in the case of CaCO₃), to form calcium oxide.

CaCO₃ → CaO + CO₂

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.

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Uses

The main use of calcium carbonate is in the construction industry, either as a building material in its own right (e.g. marble) or as an ingredient of cement.

Calcium carbonate is widely used in the pharmaceutical industry, either as an antacid or as a base material for tablets of other pharmaceuticals.

Calcium carbonate is known as whiting in ceramics/glazing applications, where it is used as a common ingredient for many glazes in its white powdered form. When a glaze containing this material is fired in a kiln, the whiting acts as a flux material in the glaze.

It is also the main component of blackboard chalk.

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