Two reactions share the intermediate species C

CHEMISTRY · Single correct · AP · Chemistry · Thermodynamics and Electrochemistry · Thermodynamics and Electrochemistry

Problem

Two reactions share the intermediate species C. Reaction 1: A + B →\rightarrow C ΔG∘=+25 kJ\Delta G^{\circ}=+25\,\text{kJ} Reaction 2: C →\rightarrow D + E ΔG∘=−50 kJ\Delta G^{\circ}=-50\,\text{kJ} Which statement best explains why the overall process A + B →\rightarrow D + E can proceed under standard conditions? (a) Because C is continuously consumed in Reaction 2, its concentration remains low, pulling Reaction 1 to the right even though the summed ΔG∘\Delta G^{\circ} is positive. (b) Reaction 2 releases heat that raises the temperature, shifting Reaction 1 toward products according to Le Châtelier’s principle. (c) The large negative ΔG∘\Delta G^{\circ} for Reaction 2 more than offsets the positive ΔG∘\Delta G^{\circ} for Reaction 1, so the sum of their ΔG∘\Delta G^{\circ} values is negative. (d) The production of two particles in Reaction 2 greatly increases entropy, making the overall ΔG∘\Delta G^{\circ} negative at the given temperature.

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