OCR A Jun 2017 Paper 1 Q20

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18 20 This question is about equilibrium reactions. (a) Hydrogen gas is manufactured by the chemical industry using the reaction of methane and steam. This is a reversible reaction, shown in equilibrium 20.1 below. equilibrium 20.1 CH4(g) + H2O(g) 3H2(g) + CO(g) H = +210 kJ mol1 Explain, in terms of le Chateliers principle, the conditions of pressure and temperature for a maximum yield of hydrogen from equilibrium 20.1, and explain why the operational conditions used by the chemical industry may be different.[4]<br /> (b) A chemist investigates the equilibrium reaction between sulfur dioxide, oxygen, and sulfur trioxide, shown below. 192SO3(g) 2SO2(g) + O2(g) The chemist mixes together SO2 and O2 with a catalyst. The chemist compresses the gas mixture to a volume of 400 cm3. The mixture is heated to a constant temperature and is allowed to reach equilibrium without changing the total gas volume. The equilibrium mixture contains 0.0540 mol SO2 and 0.0270 mol O2. At the temperature used, the numerical value for Kc is 3.045104 dm3 mol1. (i) Write the expression for Kc and the units of Kc for this equilibrium. (ii) Determine the amount, in mol, of SO3 in the equilibrium mixture at this temperature. Give your final answer to an appropriate number of significant figures. Show all your working. [2] equilibrium amount of SO3 =mol [4]<br />

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