Edexcel Jun 2013 Paper 6 Q3

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3 Glucose can be oxidized using acidified potassium manganate(VII). The kinetics of the reaction can be studied using the procedure outlined below. 1. Measured volumes of glucose solution, sulfuric acid and water were added to a conical flask. 2. A measured volume of potassium manganate(VII) solution was added to the flask. The mixture was gently swirled and a stopwatch started. 3. The time taken for the mixture in the flask to change colour was recorded and the initial rate of the reaction was then calculated. 4. The experiment was repeated using different volumes of the solutions. The results of the experiments are shown in the table below. Experiment Glucose / cm3 Sulfuric acid / cm3 A B C D 20.0 20.0 10.0 10.0 20.0 20.0 20.0 10.0 Potassium manganate(VII) / cm3 10.0 5.0 10.0 10.0 Water / cm3 Initial rate / mol dm3 s1 0.0 5.0 10.0 20.0 1.0105 5.0106 9.8106 4.9106 (2) (a) (i) Which piece of equipment should be used to measure out the volumes used in each experiment? Justify your choice.*P41653A0916* Turn over<br /> (ii) What colour change would you see in step 3? Fromto(iii) Explain why water was added to the flask in experiments B, C and D. (2) (1)(iv) Suggest a technique that could be used to continuously monitor the change in concentration of potassium manganate(VII) during the reaction. (1)(v) State the order with respect to glucose, sulfuric acid and potassium manganate(VII) and hence write the rate equation for the reaction. (3) 10 *P41653A01016*<br /> (b) Experiment A was repeated at different temperatures and the time taken for the potassium manganate(VII) to change colour was recorded. The results were processed to find values of 1/temperature and ln (rate constant) and these are shown in the table below. Experiment 1 / temperature / K1 ln (rate constant) E F G H 3.00103 3.10103 3.21103 3.35103 1.60 2.60 3.75 5.20 (i) Plot a graph of ln (rate constant) against 1 / temperature on the axes below. 1 / temperature / K1 ln (rate constant) (ii) Calculate the gradient of the graph. (3) (1) *P41653A01116* 11 Turn over<br /> (iii) Use your answer to (ii) and the relationship below to calculate the activation energy, Ea, for this reaction. Include a sign and units in your answer. Gradient = Ea R R = 8.31 J K1 mol1 (2) (Total for Question 3 = 15 marks) 12 *P41653A01216*<br />

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