Chem 2.2 Removing hardness 0.0 / 5 ? ChemistryWater hardness and solubilityGCSEAQA Created by: DanCreated on: 11-04-13 14:27 What does soft water NOT contain? Slats that can react with water to form scum 1 of 15 Does soft water produce scale? No 2 of 15 What is scale? It is Calcium carbonate and magnesium carbonate that has become insoluble 3 of 15 How has it become insoluble? Heat turns the salts from soluble to insoluble 4 of 15 What does temporary hard water contain? Hydrogen carbonate ions HCO3 5 of 15 When heated what happens to these hydrogen carbonate ions? They decompose into carbonate ions, water and CO2 6 of 15 What happens inside temporary hard water when heated? Carbonate Ions react with Magnesium and Calcium ions to form a precipitate 7 of 15 What is this method called? Precipitation 8 of 15 What is so useful about changing the magnesium and calcium ions into carbonates? Carbonate does not react with soap to form scum 9 of 15 Name another method of removing hardness? Ion-Exchange Collumns 10 of 15 Describe what happens in this process briefly? Hard water is passed through a resin turning it into soft water 11 of 15 What is in this resin? Hydrogen or sodium ions 12 of 15 Describe in terms of ions what happens within the resin? When hard water containing Mg & Ca ions is passed through the resin, they take the place of Sodium and Hydrogen ions within the resin. 13 of 15 What is the outcome? Soft water containing Sodium and Hydrogen ions 14 of 15 Why are sodium and hydrogen ions better than magnesium and calcium ions? They do not react with soap 15 of 15
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