Water
- Created by: Fionnuala Smith
- Created on: 25-03-13 10:28
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- Water
- Drinking water
- water naturally contains microorganisms & dissolved salts
- 1 passed through a filter bed to remove solid particles
- 2 chlorine gas is added to kill any harmful microorganisms
- 3 fluoride is added to drinking water in order to reduce tooth decay (too much can cause discolouration)
- Can be passed through a filter containing carbon, silver & ion exchange resins
- Any water can be distilled to produce pure water (no dissolved substances)
- water boiled then condensed (expensive & a lot of energy)
- Hard and soft water
- Soft water = not many dissolved compounds (forms a lather readily with soap)
- Hard water contains magnesium & calcium dissolved from rocks naturally
- hard water reacts with soap to scum, an oily substance, making it harder to form a lather
- soapless detergents don't form scum
- hard water reacts with soap to scum, an oily substance, making it harder to form a lather
- temp hard water contains hydrogencarbonate ions (HCO3^-)
- they decompose upon heating to produce carbonate ions (CO3^2-)
- These carbonate ions react with calcium and/or magnesium ions to form precipitates
- they decompose upon heating to produce carbonate ions (CO3^2-)
- advantages of hard water: good for health (bones & teeth & reduces risk of heart disease)
- Disadvantages of hard water: more soap is needed to form a lather (cost) & leads to deposits (scale) which reduces efficiency of systems & appliances
- Removing hardness
- dissolved magnesium & calcium ions are removed by :
- adding sodium carbonate solution (washing soda) to react to produce calcium carbonate & magnesium carbonate (insoluble precipitates out of solution)
- pass water through an ion exchange column ( resin that supplies hydrogen ions or sodium ions) As hard water passes through the resin, the calcium & magnesium ions are replaced by sodium & hydrogen ions
- dissolved magnesium & calcium ions are removed by :
- Drinking water
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