Edexcel Jan 2016 (IAL) Paper 2 Q23

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23 Solid calcium hydroxide, Ca(OH)2, is also known as slaked lime. Over one million tonnes of slaked lime are produced annually in the UK. (a) Limewater is an aqueous solution of calcium hydroxide, Ca(OH)2. Limewater is used in the laboratory as a test for carbon dioxide. (i) Suggest a value for the pH of limewater. (1)(ii) Write an equation, including state symbols, for the reaction that takes place when limewater is used to confirm the presence of carbon dioxide. (b) An aqueous solution of calcium hydroxide contains calcium ions and hydroxide ions. (i) How many moles of ions are there in one mole of calcium hydroxide? (2) (1)(ii) How many moles of electrons are there in one mole of hydroxide ions? (1)16 *P46938A01624* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br /> A E R A S I H T N I E T I R W T O N O D (c) Slaked lime (solid calcium hydroxide) can be prepared from calcium carbonate, CaCO3, in two stages. Outline how this preparation would be carried out in the laboratory. Include an equation for each stage. State symbols are not required. You do not need to include any details of apparatus in your answer, but you should mention any essential conditions. (4)A E R A S I H T N I E T I R W T O N O D A E R A S I H T N I E T I R W T O N O D(d) Coal-fired power stations produce sulfur dioxide, SO2. This pollutant gas is toxic and causes acid rain. (i) The sulfur dioxide combines with water and oxygen in the atmosphere to produce sulfuric acid, H2SO4. Write a balanced equation, including state symbols, for this overall reaction. (ii) One way to lower the amount of sulfur dioxide emissions is to pass the waste gas through a fine powder of calcium oxide, CaO(s). Explain why calcium oxide would be expected to react with sulfur dioxide. (2) (1)*P46938A01724* 17 Turn over<br /> (iii) State one other environmental problem associated with coal-fired power stations. Identify the substance which causes this problem. (2)(Total for Question 23 = 14 marks) TOTAL FOR SECTION B = 38 MARKS 18 *P46938A01824* D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A D O N O T W R I T E I N T H I S A R E A<br />

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