AQA Jan 2012 Paper 2 Q5

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do not write outside the box iodine reacts with concentrated nitric acid to produce nitrogen dioxide no a i give the oxidation state of iodine in each of the following i hio marks a ii complete the balancing of the following equation i hno hio no h o mark b in industry iodine is produced from the nalo that remains after sodium nitrate has been crystallised from the mineral chile saltpetre the final stage involves the reaction between nalo and nal in acidic solution half equations for the redox processes are given below io e h l h o l l e use these half equations to deduce an overall ionic equation for the production of iodine by this process identify the oxidising agent overall ionic equation the oxidising agent marks wmp jan chem do not write outside the box c when concentrated sulfuric acid is added to potassium iodide solid sulfur and a black solid are formed c i identify the black solid mark c ii deduce the half equation for the formation of sulfur from concentrated sulfuric acid mark d when iodide ions react with concentrated sulfuric acid in a different redox reaction the oxidation state of sulfur changes from to the reduction product of this reaction is a poisonous gas that has an unpleasant smell identify this gas mark e a yellow precipitate is formed when silver nitrate solution acidified with dilute nitric acid is added to an aqueous solution containing iodide ions e i write the simplest ionic equation for the formation of the yellow precipitate mark e ii state what is observed when concentrated ammonia solution is added to this precipitate mark e iii state why the silver nitrate is acidified when testing for iodide ions mark question continues on the next page turn over wmp jan chem do not write outside the box f consider the following reaction in which iodide ions behave as reducing agents cl aq i aq i aq cl aq f i in terms of electrons state the meaning of the term reducing agent mark f ii write a half equation for the conversion of chlorine into chloride ions mark f iii suggest why iodide ions are stronger reducing agents than chloride ions marks extra space wmp jan chem

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