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  • Water
    • Hard water and soft water
      • many compounds can dissolve in water. The amount of water present determines whether water is Soft or Hard.
      • Hard water contains magnesium and calcium ions which dissolve in natural water that flows over rocks that contain compounds of these elements.
      • The dissolved subrstances react with soap to form scum - harder to form a lather.
      • Advantages of Hard water - good for health  and reduce the development of heart disease
      • Disadvantages of hard water - more soap needed to form a lather, scale reduces efficiency of appliances.
    • There are 2 types of hard water - Temporary and Permanent
      • Permanent hard water contains a calcium salt which cannot be removed by boiling.
        • Hardness of water can be measured by titration with soap solution.
    • Removing hardness
      • Remove the dissolved calcium and magnesium ions
      • Add sodium carbonate solution.
        • The carbonate ions react with the calcium/magnesium ions to form a carbonate.
          • Precipitate out of the solution. (insoluble)
      • Pass the water through an ion exchange resin
        • Contains a resin which contains hydrogen or sodium ions.
          • the calcium/magnesium ions are replaced by hydrogen or sodium ions
          • Resin has to be replaced when it runs of our H and Na
    • Purifying water
      • Need to produce water that is good quality and safe to drink
      • An appropriate water source
      • pass through a filter bed to remove any solid particles
        • Add chlorine gas or ozone to kill any harmful bacteria
      • Remove dissolved substances by passing the water through a filter containing carbon, silver and ion exchange resins
      • distillation
  • Advantages of Hard water - good for health  and reduce the development of heart disease


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