A gas-phase reaction has and

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

Problem

A gas-phase reaction has ΔH∘=+145 kJ mol−1\Delta H^{\circ}=+145\,\text{kJ mol}^{-1} and ΔS∘=+220 J mol−1 K−1\Delta S^{\circ}=+220\,\text{J mol}^{-1}\,\text{K}^{-1}. Which statement about the reaction’s thermodynamic favorability is most accurate? (Assume the quoted values are nearly temperature-independent.) (a) It is favored at 298 K298\,\text{K} because TΔS∘T\Delta S^{\circ} already exceeds ΔH∘\Delta H^{\circ} at that temperature. (b) It is not favored at 1000 K1000\,\text{K} because the endothermic enthalpy term outweighs the entropy term at high temperature. (c) It becomes favored only at temperatures greater than about 660 K660\,\text{K} and is not favored below that temperature. (d) It is never favored because a positive enthalpy change always prevents spontaneity.

Related theory

Browse the problem library