Question

question 2 of 25
under what conditions is δg for a reaction always positive?
a. when δh and δs are both negative
b. when δh and δs are both positive
c. when δh is positive and δs is negative
d. when δh is negative and δs is positive

Explanation:

The Gibbs - free energy change is given by the formula $\Delta G=\Delta H - T\Delta S$, where $T$ (temperature) is always positive in Kelvin. When $\Delta H> 0$ (endothermic) and $\Delta S<0$ (decrease in entropy), $\Delta G=\Delta H - T\Delta S$. Since $\Delta H$ is positive and $-T\Delta S$ is also positive (because $\Delta S$ is negative), $\Delta G$ will always be positive.

Answer:

C. When $\Delta H$ is positive and $\Delta S$ is negative