CIE Mar 2017 v3 Paper 3 Q2

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You will carry out a second experiment to determine the concentration of hydrogen peroxide, FA 1, in mol dm3, by titration with acidified aqueous potassium manganate(VII). The equation for the reaction is given below. 2MnO4 (aq) + 5H2O2(aq) + 6H+(aq) 2Mn2+(aq) + 8H2O(l) + 5O2(g) PMT FA 1 is a solution of hydrogen peroxide, H2O2. FA 3 is 0.0300 mol dm3 potassium manganate(VII), KMnO4. FA 4 is dilute sulfuric acid. (a) MethodFill the burette with FA 3. Pipette 25.0 cm3 of FA 1 into a conical flask. Use the 25 cm3 measuring cylinder to add approximately 20 cm3 of FA 4 to the conical flask. Perform a rough titration and record your burette readings in the space below. The rough titre iscm3. Carry out as many accurate titrations as you think necessary to obtain consistent results. Make certain any recorded results show the precision of your practical work. Record, in a suitable form below, all of your burette readings and the volume of FA 3 added in each accurate titration. II III IV VI VII [7] (b) From your accurate titration results, obtain a suitable value for the volume of FA 3 to be used in your calculations. Show clearly how you obtained this value. 25.0 cm3 of FA 1 requiredcm3 of FA 3. [1]UCLES 2017 9701/33/F/M/17 [Turn over<br /> PMT (c) Calculations Show your working and appropriate significant figures in the final answer to each step of your calculations. (i) Calculate the number of moles of manganate(VII) ions present in the volume of FA 3 calculated in (b). (ii) Calculate the number of moles of hydrogen peroxide present in 25.0 cm3 of FA 1. moles of MnO4=mol (iii) Using your answer to (ii) calculate the concentration, in mol dm3, of hydrogen peroxide in FA 1. moles of H2O2 =mol concentration of H2O2 in FA 1 =mol dm3 [4] [Total: 12]UCLES 2017 9701/33/F/M/17<br />

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