Question

Given that $\Delta G=\Delta H-T\Delta S$, how is the spontaneity of an endothermic reaction expected to change with decreasing $T$?

• A. Becomes less spontaneous
• B. Becomes more spontaneous
• C. Does not change
• D. Decreases at first but then increases
• E. Insufficient information to make a conclusion

Answer 1

Answer: (E)

Insufficient information to make a conclusion

For an endothermic reaction, $\Delta H$ is positive. And for spontaneity $\Delta G$ should be negative. Now, if temperature $T$ is decreased but it has a positive value, whether $\Delta G$ should be negative or not will depend on the value of $\Delta S$ (whether $\Delta S$ is positive or not).

If temperature $T$ is decreased and has a negative value, then again, whether $\Delta G$ should be negative or not will depend on the value of $\Delta S$ (whether $\Delta S$ is positive or not).

Because in both the cases $\Delta H$ is positive, so whether $\Delta G$ should be negative or not will depend on the value of $\Delta S$.

Thus, option E is the correct answer. The information is insufficient to make a conclusion.