At what temperature will a reaction be spontaneous? ΔH = +22.2 kJ/mol and ΔS = +81.1 J/K-mol and assume both do not vary with temperature.

Question

Quizplus · Accepted Answer

For a reaction to be spontaneous, the Gibbs free energy change (ΔG) should be negative.

ΔG = ΔH - TΔS

At what temperature will the reaction be spontaneous?
ΔG = 0 (because the reaction is at equilibrium).
0 = ΔH - TΔS
T = ΔH/ΔS = (+22.2 kJ/mol)/(+81.1 J/K-mol) = 273 K

Since ΔH and ΔS do not vary with temperature, the value of T at which the reaction becomes spontaneous is constant.

Since T should be less than 273 K for the reaction to be spontaneous, the correct answer is D) at T > 274 K.

At What Temperature Will a Reaction Be Spontaneous? ΔH =