AQA Chemistry (2013) Unit 3

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  • Created by: Lex
  • Created on: 15-05-13 13:05

3.2.1 Hard Water

·         Soft water forms a thick lather easily

·         Hard water is harder to form a lather

·         Dissolved compounds react with soap to form scum

o   Sodium stearate (soap) + Ca2+ = calcium stearate (scum) + Na+ ions

·         Dissolved calcium and magnesium ions

·         Limestone causes hardness

o   CO2 dissolved in water – acidic

o   CaCO3 (s) + H2O (l) + CO2 (aq) = Ca2+ (aq) + 2HCO3- (aq)

o   Ca2+  causes hardness

·         Hard water leads to limescale

o   Happens in kettles

o   Scale is a poor conductor of energy

o   Costs more to heat the kettle

·         Advantages

o   Calcium helps development of bones and teeth

o   Hard water helps reduce heart disease

3.2.2 Removing Hardness

·         Remove calcium and magnesium ions

·         Temporary hardness



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