Water

Water

1. Measuring hardness

   • Titration with soap solution
     • Volume of water is put into conical flask
     • Soap solution is added to it from burette or pipette.
     • mixture is swirled to help it form lather.
     • Volume of soap solution that needs to be added to form permanent lather is recorded
     • The harder the water, the greater the volume of soap solution needed
   • Types of hardness
     • Temporary hard water can be softened by boiling it
     • Permanent hard water stays hard, even when it is boiled.
   • Explaining temporary hardness
     • Temporary hard water contains dissolved hydrogen carbonate ions, HCO3–
       • heated ions decompose (break down) to form carbonate ions, CO32–
         • carbonate ions in the boiled water react with dissolved calcium and magnesium ions to form insoluble precipitates (calcium carbonate and magnesium carbonate).
     • Permanent hard water contains dissolved sulfate ions, SO42–
       • don't decompose when heated.
         • Remain dissolved & don't react with calcium and magnesium ions - water stays hard even when boiled.

2. Hard water

   • Benefits
     • Can improve the taste of the water
     • good for the development and maintenance of bones and teeth
     • can help to reduce heart disease
   • Drawbacks
     • More soap needed to produce lather, which increases costs.
     • scum produced is unsightly - spoiling appearance of baths and shower screens, for example.
     • limescale (a solid containing calcium carbonate) is produced when the water is heated. It coats the heating element in kettles, and the inside of boilers and hot water pipes.

3. Softening hard water

   • Adding sodium carbonate to water
   • Using ion exchange columns

4. Supplying safe water

   • choose appropriate source of water
   • filter water
     • Water is purified by filtration, sedimentation and the addition of chlorine
   • chlorinate water
     • Chlorine kills microbes

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