Hardness of Water-C6

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  • Created by: Shannon
  • Created on: 29-05-13 13:18
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  • Hardness of Water
    • Calcium hydrogencarb-onate dissolves to form temporary water hardness
      • Calcium carbonate+ carbon dioxide ---> calcium hydrogencarb-onate
    • Permanent hardness-calcium sulphate rock dissolves
      • Not affected by heating
        • Ion exchange resin-water flows over solid resin-trap calcium ions and exchange them for sodium ions
          • CaSO4+ NaCO3 ---> Na2SO4+ CaCO3
    • Thermal decompostio-n softens temporary hardness
      • Ca(HCO3)2 ---> CaCO3+CO2+H2O
    • Washing soda softens temporary and permanent water hardness
      • Reacts with calcium sulphate- "locking up" calcium ions-insoluble calcium carbonate is made
    • Temporary hardness is removed by boiling- hydrogen carbonate decomposes in hot water to form limescale (calcium carbonate) water and CO2
    • Measured by a lather (number of flakes needed- a measure of water hardness)
      • Soap is shaken in water-calcium ions react-scum
        • Soap reacts with all calcium ions. More soap=stable lather


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