Sulfur trioxide is produced industrially by the reversible reaction 2 , SO_2(g) +…

CHEMISTRY · Multi-part · A Level · Chemistry · Kinetics · Kinetics

Problem

Sulfur trioxide is produced industrially by the reversible reaction 2 SO2(g)+O2(g)⇌2 SO3(g)2\,\mathrm{SO_2(g)} + \mathrm{O_2(g)} \rightleftharpoons 2\,\mathrm{SO_3(g)} The equilibrium constant KpK_p has the following measured values: • Kp=0.48K_p=0.48 at 800 K • Kp=0.14K_p=0.14 at 1000 K Assume R=8.314 J mol−1K−1R = 8.314\,\text{J mol}^{-1}\text{K}^{-1}. (a) Calculate the enthalpy change ΔH\Delta H (in kJ mol−1^{-1}) for the forward reaction, treating ΔH\Delta H as temperature-independent over this range. (b) Identify whether the forward reaction is exothermic or endothermic and explain how your result in part (a) supports your conclusion. (c) An engineer proposes lowering the reactor temperature from 900 K to 850 K at constant total pressure to increase SO3\mathrm{SO_3} yield. Predict qualitatively how this temperature change will affect the equilibrium mole fraction of SO3\mathrm{SO_3}. Justify your prediction in terms of thermodynamics and equilibrium behavior.

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