The signs of ΔG,ΔH,and ΔS at 25°C are shown below for three reactions.
Which reaction could go in the reverse direction at high temperature?

Question

The signs of ΔG,ΔH,and ΔS at 25°C are shown below for three reactions. 
Which reaction could go in the reverse direction at high temperature?

Quizplus · Accepted Answer

In order for a reaction to be spontaneous in the reverse direction at high temperature, ΔG must be negative. Only Reaction III has a negative ΔS and a positive ΔH at 25°C, which gives a positive ΔG at this temperature. However, as the temperature increases, the TΔS term becomes more significant, and at high temperature, it may overcome the positive ΔH, resulting in a negative ΔG. Therefore, only Reaction III could go in the reverse direction at high temperature.

The Signs of ΔG,ΔH,and ΔS at 25°C Are Shown Below