AQA Specimen Paper 1 Q4

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Many chemical processes release waste products into the atmosphere. Scientists are developing new solid catalysts to convert more efficiently these emissions into useful products, such as fuels. One example is a catalyst to convert these emissions into methanol. The catalyst is thought to work by breaking a HH bond. An equation for this formation of methanol is given below. CO2(g) + 3H2(g) CH3OH(g) + H2O(g) H = 49 kJ mol1 Some mean bond enthalpies are shown in Table 2. Table 2 Bond Mean bond enthalpy / kJ mol1 C=O 743 CH 412 CO 360 OH 463 Use the enthalpy change for the reaction and data from Table 2 to calculate a value for the HH bond enthalpy. [3 marks] HH bond enthalpy = kJ mol1 A data book value for the HH bond enthalpy is 436 kJ mol1. Suggest one reason why this value is different from your answer to Question 4.1. [1 mark] 0 4 . 1 . 2 0 4 Barcode Typesetter code<br /> Suggest one environmental advantage of manufacturing methanol fuel by this reaction. [1 mark] Use Le Chatelier's principle to justify why the reaction is carried out at a high pressure rather than at atmospheric pressure. [3 marks] . 3 0 4 . 4 0 4 . 5 0 4 Suggest why the catalyst used in this process may become less efficient if the carbon dioxide and hydrogen contain impurities. [1 mark] Question 4 continues on the next page Barcode Typesetter code Turn over <br /> 10 . 6 0 4 In a laboratory experiment to investigate the reaction shown in the equation below, 1.0 mol of carbon dioxide and 3.0 mol of hydrogen were sealed into a container. After the mixture had reached equilibrium, at a pressure of 500 kPa, the yield of methanol was 0.86 mol. [7 marks] CO2(g) + 3H2(g) CH3OH(g) + H2O(g) Calculate a value for Kp Give your answer to the appropriate number of significant figures. Give units with your answer. Kp = Units = Barcode Typesetter code<br /> 11 Turn over for the next question DO NOT WRITE ON THIS PAGE ANSWER IN THE SPACES PROVIDED Barcode Typesetter code Turn over <br />

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