Calcium & Its Compounds

Introduction to Calcium

Calcium is a soft, grey metal that is an essential part of bones and teeth. It is the fifth most abundant element in the Earth's crust and is found in many minerals.

Calcium compounds are widely used in various industries and have significant biological importance.

Common Calcium Compounds

• Calcium Carbonate (CaCO₃): Found in rocks as limestone and marble. Used in the manufacture of cement and lime, and as a calcium supplement.
• Calcium Oxide (CaO): Also known as quicklime, it is used in the steel industry, for water treatment, and in the production of cement.
• Calcium Sulfate (CaSO₄): Exists as gypsum and is used in plaster and as a drying agent.

Properties of Calcium Compounds

Compound	Properties	Uses
Calcium Carbonate (CaCO3)	White, insoluble in water, reacts with acids to produce carbon dioxide	Construction, antacids, agricultural lime
Calcium Oxide (CaO)	White, caustic, reacts with water to form calcium hydroxide	Steelmaking, cement production, chemical industry
Calcium Sulfate (CaSO4)	White, slightly soluble in water	Plaster of Paris, drywall, soil conditioner

Reactions Involving Calcium Compounds

• Calcium Carbonate:
  • Thermal decomposition: $$\text{CaCO}_3 \rightarrow \text{CaO} + \text{CO}_2$$ This reaction is used in the production of lime.
  • Reaction with acids: $$\text{CaCO}_3 + 2\text{HCl} \rightarrow \text{CaCl}_2 + \text{CO}_2 + \text{H}_2\text{O}$$ Produces carbon dioxide gas.
• Calcium Oxide:
  • Reaction with water: $$\text{CaO} + \text{H}_2\text{O} \rightarrow \text{Ca(OH)}_2$$ This reaction releases heat and forms slaked lime.