AQA Jun 2012 Paper 2 Q1

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section a answer all questions in the spaces provided do not write outside the box a student carried out an experiment to determine the rate of decomposition of hydrogen peroxide into water and oxygen gas the student used cm of a mol dm solution of hydrogen peroxide at k and measured the volume of oxygen collected curve r in each of figures and shows how the total volume of oxygen collected changed with time under these conditions a draw a curve on figure to show how the total volume of oxygen collected will change with time if the experiment is repeated at k using cm of a mol dm solution of hydrogen peroxide figure volume of oxygen cm time s marks b draw a curve on figure to show how the total volume of oxygen collected will change with time if the experiment is repeated at k using cm of a mol dm solution of hydrogen peroxide figure time s volume of oxygen cm marks wmp jun chem do not write outside the box c draw a curve on figure to show how the total volume of oxygen collected will change with time if the original experiment is repeated at a temperature higher than k you should assume that the gas is collected at a temperature of k figure volume of oxygen cm time s marks d explain why the slope gradient of curve r decreases as time increases marks extra space question continues on the next page turn over wmp jun chem do not write outside the box e the student discovered that hydrogen peroxide decomposes at a faster rate when a few drops of aqueous hydrogen bromide are added to the solution the student found on the internet that this decomposition is thought to proceed in two steps as shown by the following equations step h o hbr hbro h o step hbro h o h o o hbr e i write an equation for the overall reaction mark e ii give one reason other than the increase in rate of reaction why the student was able to deduce that hydrogen bromide behaves as a catalyst in this two step reaction mark wmp jun chem turn over for the next question do not write on this page answer in the spaces provided turn over wmp jun chem

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