Above what temperature does the following reaction become nonspontaneous?
N₂(s) + 3 H₂(g) → 2 NH₃(g) ΔH = -92.22 kJ; ΔS = -198.75 J/K

Question

Above what temperature does the following reaction become nonspontaneous? N₂(s)+ 3 H₂(g)→ 2 NH₃(g)ΔH = -92.22 kJ; ΔS = -198.75 J/K

Quizplus · Accepted Answer

We can use the Gibbs free energy equation to solve this problem:
ΔG = ΔH - TΔS
At the temperature when ΔG becomes zero, the reaction becomes nonspontaneous. So we can set ΔG = 0 and solve for T:
0 = -92.22 kJ - T(-198.75 J/K)
T = 464 K
Therefore, above 464 K, the reaction becomes nonspontaneous. The answer is choice C.

Above What Temperature Does the Following Reaction Become Nonspontaneous