Calcium & its Compounds | Chemistry for JAMB PDF Download

Alkaline-Earth Metals

• Alkaline-earth metals are a group of elements in the periodic table, including beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
• This note will focus on calcium and its compounds.

Calcium

• Calcium (Ca) is a silvery-white, alkaline-earth metal with the atomic number 20 and symbol Ca.
• It is the fifth most abundant element in the Earth's crust and commonly found in minerals such as limestone, gypsum, and fluorite.

Properties and Uses of Calcium

• Calcium is a soft metal that can be easily cut with a knife.
• It has a relatively low melting point and density.
• Calcium has a high reactivity with water and oxygen, and it rapidly forms an oxide layer on its surface when exposed to air.
• It exhibits a strong affinity for oxygen, and hence, it is stored under oil or inert gases.
• Calcium is an excellent conductor of electricity.
• Calcium compounds are widely used in various industries, including construction, agriculture, and medicine.

Common Calcium Compounds

Calcium Oxide (Quicklime):

• Chemical Formula: CaO
• Calcium oxide is a white, caustic, and alkaline solid.
• It is obtained by heating calcium carbonate (e.g., limestone) in a process called calcination.
• Quicklime is widely used in the construction industry for making mortar and cement, as well as in the production of glass, paper, and steel.

Calcium Hydroxide (Slaked Lime):

• Chemical Formula: Ca(OH)₂
• Calcium hydroxide is a white, crystalline compound with a low solubility in water.
• It is produced by reacting calcium oxide with water.
• Slaked lime has various applications, including in the preparation of building materials, as a pH regulator in water treatment, and in the production of chemicals.

Calcium Trioxocarbonate (IV) (Calcium Carbonate):

• Chemical Formula: CaCO₃
• Calcium carbonate is a white, insoluble solid that occurs naturally in rocks, shells, and coral reefs.
• It is commonly found in the form of limestone, chalk, or marble.
• Calcium carbonate has numerous uses, including in the manufacturing of cement, ceramics, paints, and dietary supplements.

Preparation of Calcium Oxide from Sea Shells

• Sea shells are primarily composed of calcium carbonate.
• To obtain calcium oxide from sea shells, the following steps can be followed:
  • Crush the sea shells into small pieces.
  • Heat the crushed sea shells strongly in a furnace or kiln.
  • The heat causes the calcium carbonate in the shells to decompose, resulting in the formation of calcium oxide and the release of carbon dioxide gas.
  • Collect the calcium oxide, also known as quicklime, for further use in various applications.

Note: It is important to exercise caution while handling calcium oxide, as it is highly reactive and can cause burns or irritation upon contact with skin or eyes. Protective equipment, such as gloves and goggles, should be worn when working with calcium oxide.