ACS Chemistry Practice Exam 2026 – The All-in-One Guide to Exam Success!

When considering the values of ∆H (enthalpy change), ∆S (entropy change), and their influence on ∆G (Gibbs free energy change), the relationship is described by the equation:

∆G = ∆H - T∆S

In this instance, a negative ∆H indicates that the reaction is exothermic and releases heat, while a positive ∆S suggests a favorable increase in disorder or randomness in the system. Since ∆H is negative and ∆S is positive, this combination favors spontaneity.

For the reaction to occur spontaneously, ∆G must be negative. A negative value of ∆G indicates that the process can occur without additional energy input. The positive entropy (∆S) contributes to making ∆G negative, especially at higher temperatures where the T∆S term (temperature multiplied by the change in entropy) becomes significant.

Therefore, the correct choice indicating that ∆G is negative under these conditions best reflects that the reaction will occur spontaneously. The answer acknowledges that the reaction is indeed thermodynamically favorable due to the conditions of negative enthalpy and positive entropy.