For the reaction, A+B⇌C+D ∆G∘=∆H∘−T∆S∘ The reaction will be spontaneous when, ∆G∘<0, i.e. |T∆S∘|>|∆H∘| [ Given,∆H∘=80kJmol−1;∆S∘=2TJmol−1K−1] ⇒T‌>‌
|∆H∘|
|∆S∘|
⇒T>‌
80×1000Jmol−1
2TJmol−1K−1
T2‌>4×104K⇒T>200K So, the minimum temperature (T) at which the reaction will be spontaneous is 200K.