OCR A Jan 2012 Paper 5 Q7

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7 Dinitrogen tetroxide, N2O4(g), and nitrogen dioxide, NO2(g), coexist in the following equilibrium. 18 2NO2(g) N2O4(g) H = 57 kJ mol1 A chemist adds 4.00 mol NO2 to a container with a volume of 2.00 dm3. The container is sealed, heated to a constant temperature and allowed to reach equilibrium. The equilibrium mixture contains 3.20 mol NO2. (a) Calculate the value for Kc under these conditions. [5]OCR 2012<br />
 (b) The experiment is repeated but the pressure in the container is doubled. 19 Explain in terms of Kc the effect on the concentrations of NO2 and N2O4 when the mixture has reached equilibrium.[3] [Total: 8]OCR 2012 Turn over<br />

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