Question

For a chemical reaction to be spontaneous at all temperatures, which of the following conditions must be met?
A. ?S° > 0, ?H° > 0.
B. ?S° > 0, ?H° < 0.
C. ?G° > 0.
D. ?S° < 0, ?H° > 0.
E. ?S° < 0, ?H° < 0.

Answer 1

Answer:

B. S° > 0, ?H° < 0.

Explanation:

Expression for change in free energy is

     ΔG = ΔH - TΔS

For a reaction to be spontaneous , ΔG should be negative . When we watch the relation above , we find that for  ΔG will be negative at any temperature , if ΔH is negative and  ΔS is positive . Then both the terms on the right hand side will be negative and then   ΔG will become negative.

So option B is correct .