Calcium carbonate

Calcium carbonate is a chemical compound made of calcium and carbonate ions, with the chemical formula CaCO₃. The elements involved are calcium (Ca), carbon (C), and oxygen (O). It is a common substance found as rock in all parts of the world, and is the main component of seashells, snails, and eggshell.

Calcium carbonate

Travertine calcium carbonate deposits from a hot spring

Calcium carbonate is usually the main cause of hard water. It is used as a calcium supplement or as a treatment for antacid (brand name Tums), but too much can be bad for your health.

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

• Aragonite
• Calcite
• Vaterite or (μ-CaCO₃)
• Chalk
• Limestone
• Marble
• Travertine

Reactions with acids

Calcium carbonate reacts with strong acids (like hydrochloric acid) to make calcium salt, water, and carbon dioxide. It can also react with weak acids (like acetic acid) but less quickly. All of the rocks and minerals mentioned above will react with acids.

The balanced chemical equation of calcium carbonate and hydrochloric acid reaction is:

CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂

The word chemical equation for the hydrochloric acid reaction is:

Calcium carbonate + 2 Hydrochloric acid → Calcium chloride + Water + Carbon dioxide

While the balanced chemical equation of calcium carbonate and acetic acid reaction is:

CaCO₃ + 2CH₃COOH → Ca(CH₃COO)₂ + H₂O + CO₂

And the word chemical equation for the acetic acid reaction is:

Calcium carbonate + 2 Acetic acid → Calcium acetate + Water + Carbon dioxide

This is why a rock or mineral might need to be added with an acid to check there is calcium carbonate or not. If there is, then it will fizz and make carbon dioxide. But if it does not, then it will not fizz because there is no carbon dioxide forming.

Related pages

• Ocean acidification
• Gesso
• Cuttlefish
• Cuttlebone