For the reaction the enthalpy change is and the entropy change is

CHEMISTRY · Single correct · A Level · Chemistry · Thermodynamics · Thermodynamics

Problem

For the reaction C2H5OH(l)→C2H4(g)+H2O(g)\text{C}_2\text{H}_5\text{OH}(l)\rightarrow\text{C}_2\text{H}_4(g)+\text{H}_2\text{O}(g) the enthalpy change is ΔH∘=−75.0 kJ mol−1\Delta H^{\circ}=-75.0\,\text{kJ mol}^{-1} and the entropy change is ΔS∘=−165 J mol−1 K−1\Delta S^{\circ}=-165\,\text{J mol}^{-1}\,\text{K}^{-1}. At approximately what temperature will the reaction shift from being favored to being unfavored? (Assume both quantities are temperature-independent.) (a) 530 K530\,\text{K} (b) 455 K455\,\text{K} (c) 273 K273\,\text{K} (d) It will be unfavoured at all temperatures because both ΔH∘\Delta H^{\circ} and ΔS∘\Delta S^{\circ} are negative.

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