AQA Chemistry Hardness of Water 3.0 / 5 based on 1 rating ? ChemistryWater hardness and solubilityGCSEAQA Created by: BenjaminCreated on: 01-04-13 16:51 Wich two substances does hard water form? Scum and scale 1 of 21 How does the time it takes for a quality lather to form in hard water differ for the time it takes to form in soft water from an ordinary bar of soap Hard water: A long time , Soft water: Very fast 2 of 21 Name the ions that are present in hard water Calcium and Magnesium 3 of 21 When calcuim and magnesium react with soap wich insoluble substance do they form? Scum 4 of 21 When hard water is heated, what does it form, and what is this substance mainly made up of? Sale, mostly calcium carbonate 5 of 21 Explain why kettle heating elements with a build up of scale are not very efficient Scale is a thermal insulator, Kettle takes longer to boil, becomes less effiecent 6 of 21 What charges are present on the Calcium and Magnesium Ions 2+ 7 of 21 Watch a video on rain falling onto limestone, chalk... and how this makes the water hard :) 8 of 21 Give two advantages of hard water for your health Ca 2+ Ions are good for maintaining healthy bones and teeth, Reduced the risk of heart disease 9 of 21 In simple mans terms, how do we make hard water soft? By removing the Calcium and Magnesium Ions 10 of 21 State the two types of hardness Temporary and permenant 11 of 21 What is temporary hardness caused by? The Hydrogencarbonate ion, HCO3 (-1 charge) in Ca(HCO3)2 12 of 21 What is permenant hardness caused by? Dissolved calcium sulfate 13 of 21 By which process can temporary hardness be removed? By boiling 14 of 21 What happens to the calcium hydrocarbonate in temporary hard water when we boil it? It decomposes to form calcium carbonate 15 of 21 Is calcium carbonate soluble? Thus how does it effect the efficiency of kettles It is insoluble. It isn't a conductor of heat energy so it takes longer for a kettles heating element to transfer heat energy to the water. 16 of 21 Both temporary and permanent hardness can be softened. How is this done? By adding washing soda (sodium carbonate)/ Running water through an ion exchange resin 17 of 21 What is the formula for washing soda (sodium carbonate)? Na2CO3 18 of 21 When the carbonate ions in washing soda react with the calcium and magnesium ions in the hard water, what is formed? An insoluble precipitate of calcium carbonate and magnesium carbonate. 19 of 21 Watch a video on the effects of running water through an ion exchange resin :) 20 of 21 When Calcium carbonate reacts with a weak acidic solution (rain water, streams) what does it form? Calcium hydrogencarbonate 21 of 21
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