C13

  • Limestone
    • limestone is composed of calcium carbonate in the form of mineral calcite
    • marble and chalk are also made of calcite. they are a form of limestone
    • most other limestones are formed from the debris of animal structures such as brachiopods and crinoids
    • marble is made of calcium carbonate. it is formed when limestone is subjected to high pressures/ temperatures to create crystals of calcium carbonate in the rock
  • Use of limestone
    • used for:
      • making of cement
      • road building
      • glass making
      • extraction of iron
    • neutralisation of acid soil:
      • powdered limestone is most often used to neutralise acid soil because it is cheap
        • carbonate ion + hydrogen ion → carbon dioxide + water
    • Lime manufacture:
      • when calcium carbonate is heated strongly, it is thermally decomposed to form calcium oxide (lime) and carbon dioxide
      • this process takes place in a lime kiln
      • the calcium oxide produced is known as quicklime or lime
    • Uses of calcium oxide:
      • spread it on fields on neutralise soil acidity and to improve drainage of water through souls that contain large amounts of clay
      • neutralise industrial waste products such as FGD
      • drying agent in industry and in the manufacture of mouthwash