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Multiple Choice
Given ΔH°rxn = -95 kJ, ΔS°rxn = 157 J/K, and T = 855 K, calculate the change in Gibbs free energy (ΔG) and predict whether this reaction is spontaneous at the given temperature. Choose from the following options:
A
-134 kJ; spontaneous
B
2.3 x 10^2 kJ; spontaneous
C
-39 kJ; spontaneous
D
+134 kJ; nonspontaneous
Verified step by step guidance
1
Start by recalling the Gibbs free energy equation: ΔG = ΔH - TΔS.
Ensure all units are consistent. Convert ΔS°rxn from J/K to kJ/K by dividing by 1000: ΔS°rxn = 157 J/K = 0.157 kJ/K.
Substitute the given values into the Gibbs free energy equation: ΔG = (-95 kJ) - (855 K)(0.157 kJ/K).
Calculate the term TΔS: (855 K)(0.157 kJ/K) to find the value to subtract from ΔH.
Determine the sign of ΔG. If ΔG is negative, the reaction is spontaneous; if positive, it is nonspontaneous.