AQA January 2011 – Unit 4 Q1

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section a answer all questions in the spaces provided do not write outside the box the rate of hydrolysis of an ester x hcooch ch ch was studied in alkaline conditions at a given temperature the rate was found to be first order with respect to the ester and first order with respect to hydroxide ions a i name ester x mark a ii using x to represent the ester write a rate equation for this hydrolysis reaction mark a iii when the initial concentration of x was mol dm and the initial concentration of hydroxide ions was mol dm the initial rate of the reaction was x mol dm s calculate a value for the rate constant at this temperature and give its units calculation units marks a iv in a second experiment at the same temperature water was added to the original reaction mixture so that the total volume was doubled calculate the initial rate of reaction in this second experiment mark wmp jan chem do not write outside the box a v in a third experiment at the same temperature the concentration of x was half that used in the experiment in part a iii and the concentration of hydroxide ions was three times the original value calculate the initial rate of reaction in this third experiment mark a vi state the effect if any on the value of the rate constant k when the temperature is lowered but all other conditions are kept constant explain your answer effect explanation marks b compound a reacts with compound b as shown by the overall equation a b ab the rate equation for the reaction is rate k a b a suggested mechanism for the reaction is step step step b ab a ab b ab ab b ab deduce which one of the three steps is the rate determining step explain your answer rate determining step explanation marks turn over wmp jan chem do not write outside the box there are no questions printed on this page do not write on this page answer in the spaces provided wmp jan chem

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