CIE Jun 2014 v2 Paper 4 Q3

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The following four isomeric esters with the molecular formula C7H14O2 are used as arti cialavours in drinks and sweets to give a pear, banana or plum taste to foodstuffs. PMT (a) In each of the spaces below, write one or more of the letters A-D, as appropriate. (i) Which of these compounds can exist as optical isomers?(ii) On hydrolysis, which of these compounds produce(s) a secondary alcohol?[3] (b) The hydrolysis of all these compounds produces ethanoic acid, CH3CO2H, as one of the products. State the reagents and conditions needed for this hydrolysis.[1]UCLES 2014 9701/42/M/J/14 [Turn over<br /> PMT (c) The acid dissociation constant, Ka, of ethanoic acid is 1.75105 mol dm3. (i) Explain why this value of Ka is much larger than that of ethanol, CH3CH2OH,smaller than that of chloroethanoic acid, Cl CH2CO2H.(ii) Calculate the pH of a 0.100 mol dm3 solution of ethanoic acid. (d) 20.0 cm3 of 0.100 mol dm3 NaOH were slowly added to a 10.0 cm3 sample of 0.100 mol dm3 ethanoic acid, and the pH was measured throughout the addition. (i) Calculate the number of moles of NaOH remaining at the end of the addition. [4] (ii) Calculate the [OH] at the end of the addition. (iii) Using the expression Kw = [H+][OH] and your value in (ii), calculate [H+] and the pH of the solution at the end of the addition.UCLES 2014 9701/42/M/J/14<br /> (iv) On the following axes, sketch how the pH will change during the addition of a total of 20.0 cm3 of 0.100 mol dm3 NaOH. Mark clearly where the end point occurs. PMT 14 pH 5 15 volume NaOH added / cm3 10 20 (v) From the following list of indicators, put a tick in the box by the side of the indicator you consider most suitable for this titration. indicator pH at which colour changes place one tick only in this column malachite green thymol blue bromophenol blue thymolphthalein 0 - 1 1 - 2 3 - 4 9 - 10 [7] [Total: 15]UCLES 2014 9701/42/M/J/14 [Turn over<br />

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