Calcium Carbonate

**Molecular formula:** CaCO₃

**Molar mass:** 100,086 g/mol

**Information:** Calcium carbonate is a white, crystalline substance very little soluble in water. It is an ionic compound containing a calcium cation Ca²⁺ and carbonate anion CO₃²⁻. When the water contains carbon dioxide, it dissolves to form calcium bicarbonate (CaCO₃+ CO₂ + H₂O → Ca(HCO₃)₂). The reaction takes place backwards and is the basis for the formation of stalactites.

**Use:** Used as a fertilizer. It has a significant use in the construction industry. Its heat decomposition (CaCO₃ → CaO + CO₂) produces calcium oxide (burnt lime) which after reaction with water (CaO + H₂O → Ca(OH)₂) is converted to calcium hydroxide (slaked lime). Slag lime is used for lime mortar (a mixture of slaked lime, sand and water).

**Occurrence:** In nature, CaCO₃, which is made from calcium and aragonite minerals, is found in the form of limestone rocks.