Calcium carbonate

Calcium carbonate (CaCO₃) is a common chemical compound found in rocks, shells, and bones. It’s a white, odourless powder or crystal that plays important roles in nature, industry, and even medicine.

Basic Properties

• Chemical formula: CaCO₃

• Molar mass: 100.09 g/mol

• Appearance: White solid (powder or crystals)

• Solubility in water: Very low (~0.0013 g/100 mL at 25°C)

Natural Occurrence

Calcium carbonate is the main component of:

• Limestone

• Chalk

• Marble

• Seashells and coral

• Eggshells and pearls

It forms through biological and geological processes, often by marine organisms that use it to build their shells and skeletons.

Uses of Calcium Carbonate

Industry Application Construction: Cement, lime production, building stone

Agriculture: Soil pH adjustment (agricultural lime)

Medicine: Antacid for heartburn, calcium supplement

Plastics & Paper: Filler material to improve brightness and finish

Food Industry: Additive (E170) in toothpaste, chewing gum, and baking powder

Chemical Reactions

One notable reaction:
With acid (like HCl):
CaCO₃ + 2HCl → CaCl₂ + CO₂↑ + H₂O
This is why it fizzes when vinegar or lemon juice touches limestone or chalk.

Environmental Role

• Carbon Cycle: Calcium carbonate stores carbon in solid form. When it dissolves or breaks down, CO₂ is released.

• Ocean Acidification: Excess CO₂ makes oceans more acidic, dissolving CaCO₃ and threatening shell-forming marine life.