AQA Jan 2011 Paper 2 Q10

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do not write outside the box a reactions that involve oxidation and reduction are used in a number of important industrial processes iodine can be extracted from seaweed by the oxidation of iodide ions in this extraction seaweed is heated with mno and concentrated sulfuric acid a i give the oxidation state of manganese in mno mark a ii write a half equation for the reaction of mno in acid to form mn ions and water as the only products mark a iii in terms of electrons state what happens to the iodide ions when they are oxidised mark b chlorine is used in water treatment when chlorine is added to cold water it reacts to form the acids hcl and hclo the following equilibrium is established cl aq h o i h aq cl aq hclo aq b i give the oxidation state of chlorine in cl and in hclo cl hclo marks wmp jan chem b ii deduce what happens to this equilibrium as the hclo reacts with bacteria in the water supply explain your answer do not write outside the box marks extra space c concentrated sulfuric acid is reduced when it reacts with solid potassium bromide concentrated sulfuric acid is not reduced when it reacts with solid potassium chloride c i write the two half equations for the following redox reaction h br h so br so h o half equation half equation marks c ii write an equation for the reaction of solid potassium chloride with concentrated sulfuric acid mark question continues on the next page turn over wmp jan chem c iii explain why chloride ions are weaker reducing agents than bromide ions do not write outside the box marks extra space end of questions copyright aqa and its licensors all rights reserved wmp jan chem

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