OCR A Jan 2013 Paper 5 Q5

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5 Methanol can be prepared industrially by reacting together carbon monoxide and hydrogen. This is a reversible reaction: 12 CO(g) + 2H2(g) CH3OH(g) H = 94 kJ mol1A chemist mixes together 0.114 mol CO(g) and 0.152 mol H2(g) in a container. The container is pressurised and then sealed. The total volume is 200 cm3. The mixture is heated to 500 K and left to reach equilibrium. The volume of the sealed container is kept at 200 cm3. The chemist analyses the equilibrium mixture and finds that 0.052 mol CH3OH has formed. (a) Calculate the value of Kc, including units, for the equilibrium at 500 K. Give your answer to three significant figures. Kc =units[6]OCR 2013<br /> 13 (b) The chemist repeats the experiment using the same initial amounts of CO and H2. The same procedure is used but the mixture is heated in the 200 cm3 sealed container to a higher temperature than 500 K. As the gas volume is kept at 200 cm3, the increased temperature also increases the pressure. Explain why it is difficult to predict how the yield of CH3OH would change. Explain what happens to the value of Kc.[4] [Total: 10]OCR 2013 Turn over<br />

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