Calcium carbonate (CaCO₃) is a chemical compound widely used in various industries. It is a white, odorless powder or crystalline solid that occurs naturally in limestone, marble, and chalk. Calcium carbonate is used in a wide range of applications due to its abundant availability, low cost, and versatility. It plays a significant role in the construction, paper, plastics, paint, and food industries, among others.
Properties of Calcium Carbonate:
- Molecular Formula: CaCO₃
- Molar Mass: 100.09 g/mol
- CAS Number: 471-34-1
- Functional Group: Carbonate group (CO₃²⁻).
- Reactivity:
- Calcium carbonate is relatively insoluble in water, but it dissolves in acidic solutions such as hydrochloric acid (HCl), producing carbon dioxide (CO₂), water, and calcium chloride (CaCl₂): CaCO3+2HCl→CaCl2+CO2+H2OCaCO₃ + 2HCl → CaCl₂ + CO₂ + H₂OCaCO3+2HCl→CaCl2+CO2+H2O
- Thermal decomposition of calcium carbonate produces calcium oxide (quicklime) and carbon dioxide at high temperatures: CaCO3→CaO+CO2CaCO₃ → CaO + CO₂CaCO3→CaO+CO2
- When exposed to heat and pressure, calcium carbonate forms lime (CaO), which is used in various industrial processes like steelmaking, water treatment, and construction.
- Appearance: A white or colorless crystalline solid.
- Odor: Odorless.
- Density: 2.71 g/cm³.
- Melting Point: Calcium carbonate decomposes before melting, at around 825°C (1517°F), to produce calcium oxide and carbon dioxide.
- Boiling Point: Calcium carbonate does not have a defined boiling point because it decomposes before boiling.
- Solubility:
- Insoluble in water but dissolves in acidic solutions, as mentioned above.
- Slightly soluble in rainwater due to the presence of dissolved carbon dioxide, forming calcium bicarbonate (Ca(HCO₃)₂).
Uses of Calcium Carbonate:
- Building Materials: Used in cement and concrete production.
- Paper: Used as a filler and coating pigment in paper manufacturing.
- Plastics: Used as a filler in plastics and rubber.
- Agriculture: Used to neutralize soil acidity and as a calcium supplement for animals.
- Food Industry: Used as a food additive (E170) and in calcium supplements.