OCR A Jun 2009 Paper 2 Q4

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In the chemical industry methanol, CH3OH, is synthesised by reacting together carbon monoxide and hydrogen in the presence of copper, zinc oxide and alumina which act as a catalyst. This is a reversible reaction. CO(g) + 2H2(g) CH3OH(g) H = 91 kJ mol1 (a) High pressures and low temperatures would give the maximum equilibrium yield of methanol. Explain why.[2] (b) Explain why the actual conditions used in the chemical industry might be different from those in (a) above.[2] (c) Catalysts are increasingly being used in chemical processes. A catalyst speeds up a reaction without being consumed by the overall reaction. A catalyst provides an alternative reaction route with a lower activation energy. (i) Chlorine radicals, Cl , catalyse some reactions. Choose a reaction that you have studied that is catalysed by chlorine radicals. Write down an equation for the overall reaction and show how chlorine radicals are not consumed by the overall reaction.[3]OCR 2009<br />
 (ii) Using the axes below, sketch an enthalpy profile diagram for an exothermic reaction to show how a catalyst provides an alternative reaction route with a lower activation energy. Include on your diagram labels for: enthalpy change, H; activation energy for the catalysed route, Ec; activation energy for the uncatalysed route, Ea. enthalpy reactants progress of reaction [3] (d) Chemical companies are using catalysts to develop processes that are more sustainable. These processes reduce costs and are less harmful to the environment. Suggest two ways in which the use of catalysts helps chemical companies to make their processes more sustainable.[4]OCR 2009 [Total: 14] Turn over<br />

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