AQA Jan 2010 Paper 4 Q2

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areas outside the box will not be scanned for marking in this question give all values of ph to decimal places a i write an expression for the term ph mark a ii calculate the concentration in mol dm of an aqueous solution of sulfuric acid that has a ph of marks b a student carried out a titration by adding an aqueous solution of sodium hydroxide from a burette to an aqueous solution of ethanoic acid the end point was reached when cm of the sodium hydroxide solution had been added to cm of mol dm ethanoic acid b i write an equation for the reaction between sodium hydroxide and ethanoic acid mark b ii calculate the concentration in mol dm of the sodium hydroxide solution used marks wmp jan chem b iii a list of indicators is shown below areas outside the box will not be scanned for marking indicator thymol blue bromophenol blue litmus cresol purple ph range select from the list the most suitable indicator for the end point of this titration mark b iv suggest why the concentration of sodium hydroxide in a solution slowly decreases when left open to air mark c at k the value of the acid dissociation constant ka for ethanoic acid in aqueous solution is mol dm c i write an expression for the acid dissociation constant ka for ethanoic acid mark c ii calculate the ph of mol dm ethanoic acid at this temperature marks extra space question continues on the next page turn over wmp jan chem areas outside the box will not be scanned for marking c iii calculate the ph of the buffer solution formed when cm of mol dm potassium hydroxide are added to cm of mol dm ethanoic acid marks extra space wmp jan chem there are no questions printed on this page do not write on this page answer in the spaces provided turn over wmp jan chem

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