Preparation of Calcium Carbonate – CaCO₃

1. CaCO₃ is obtained by using carbon dioxide and slaked lime as raw materials. When carbon dioxide is passed through slaked lime, calcite is obtained.

Another method to obtain calcite is by adding sodium carbonate to calcium chloride.

 

Ca (OH)₂ + CO₂ → CaCO₃ + H₂O

 

 

CaCl₂ + Na₂CO₃ → CaCO₃ + 2NaCl

 

When carbon dioxide is passed in excess it leads to the formation of calcium hydrogen-carbonate.

2. On a large scale, it is prepared by passing carbon dioxide gas through calcium hydroxide (slaked lime). However, if carbon dioxide is passed in excess, it forms the soluble calcium hydrogen-carbonate.

Ca(OH)₂ + CO₂→ CaCO₃ + H₂O

Properties of Calcium Carbonate – CaCO₃

• It is a fluffy powder.
• It decomposes to give carbon dioxide when heated up to 1200K.
• When it reacts with dilute acid, it liberates carbon dioxide as a by-product.

 

CaCO₃+H₂SO₄ → CaSO₄+H₂O+CO₂

 

• At 1200K, calcium carbonate decomposes to give carbon dioxide and calcium oxide.
  CaCO₃ → CaO + CO₂
• On reacting with dilute acids, calcium carbonate gives carbon dioxide.
  CaCO₃ + 2HCl → CaCl₂ + H₂O +CO₂