CIE Jun 2017 v3 Paper 2 Q3

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Sulfur trioxide, SO3, is manufactured from sulfur dioxide and oxygen by the Contact process. PMT 2SO2(g) + O2(g) 2SO3(g) H = 196.0 kJ mol1 (a) The enthalpy change of formation of SO2, Hf SO2(g), is 296.8 kJ mol1. (i) Define the term enthalpy change of formation.[2] (ii) Use the data to calculate the enthalpy change of formation of SO3(g). Hf SO3(g) =kJ mol1 [2] (b) The Contact process is usually carried out at a temperature of approximately 700 K, a pressure of approximately 150 kPa and in the presence of a vanadium(V) oxide catalyst, V2O5. The Boltzmann distribution for a mixture of SO2 and O2 at 700 K is shown. Eacat represents the activation energy for the reaction in the presence of the catalyst. proportion of molecules with a given energy Eacat molecular energy (i) Add a labelled mark, Eauncat, to the diagram to indicate the activation energy in the absence [1] of the catalyst.UCLES 2017 9701/23/M/J/17<br /> PMT (ii) State the benefit of using a catalyst in this reaction. Explain how it achieves this effect.[2] (iii) State and explain how an increase in pressure would affect both the rate of reaction and the yield of SO3 in the Contact process. rateyield[4]UCLES 2017 9701/23/M/J/17 [Turn over<br /> (c) At a pressure of 1.50105 Pa, 1.00 mol of sulfur dioxide gas, SO2, was mixed with 1.00 mol of oxygen gas, O2. The final equilibrium mixture formed was found to contain 0.505 mol of O2. 2SO2(g) + O2(g) 2SO3(g) (i) Calculate the amount, in mol, of SO2 and SO3 in the equilibrium mixture. PMT (ii) Calculate the partial pressure of oxygen gas, pO2, in the equilibrium mixture. SO2 =mol SO3 =mol [1] pO2 =Pa [2]UCLES 2017 9701/23/M/J/17<br /> (d) In another equilibrium mixture formed from different starting amounts of SO2 and O2, the partial pressures of SO2, O2 and SO3 were as shown. PMT pSO2 = 8.42102 Pa pO2 = 6.00104 Pa pSO3 = 9.10104 Pa (i) Write the expression for the equilibrium constant, Kp, for the production of SO3 from SO2 and O2. Kp = (ii) Calculate the value of Kp for this reaction and state the units. [1] Kp =units =[2] [Total: 17]UCLES 2017 9701/23/M/J/17 [Turn over<br />

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