AQA Jun 2016 Paper 5 Q9

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a do not write outside the box a student weighed out a g sample of impure k fe c o h o and dissolved it in water this solution was added to a cm volumetric flask and made up to cm with distilled water a cm portion was pipetted into a conical flask and an excess of acid was added the mixture was heated to c and titrated with mol dm kmno solution cm of kmno solution were needed for a complete reaction in this titration only the c o ions react with the kmno solution the reaction between c o explain what is meant by the term autocatalysed and identify the catalyst in the reaction marks ions is autocatalysed ions and mno b select from the list the most suitable substance used to acidify the solution in the conical flask put a tick in the correct box mark h c o h so hcl hno wmp jun chem c d the reaction between c o explain why the reaction is initially slow ions and mno ions is very slow at first do not write outside the box marks write an equation for the reaction between c o solution calculate the percentage purity of the original sample of k fe c o h o give your answer to significant figures ions and mno ions in acidic marks turn over wmp jun chem do not write outside the box e a solution of kmno has an unknown concentration describe briefly how colorimetry can be used to determine the concentration of this solution marks end of questions wmp jun chem

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