Final answer:
Yes, reactions are thermodynamically feasible if the total entropy change is positive because the sign of the Gibb's free energy change determines spontaneity, which must be negative for a process to be spontaneous.
Step-by-step explanation:
The statement that reactions are thermodynamically feasible if the total entropy change is positive is generally true. For a reaction to be spontaneous, the criterion is a positive total entropy change (∆Stotal). The spontaneity of a chemical reaction depends on the Gibb's free energy change (∆G), which is directly related to both the enthalpy change (∆H) and the entropy change (∆S) through the equation ∆G = ∆H - T∆S, where T is the absolute temperature in Kelvin. A reaction will be spontaneous if ∆G is negative.
Textbooks and teachers often mention enthalpically and entropically driven reactions to describe cases where either ∆H or the T∆S term predominates. However, this can be misleading because it is the combination of both enthalpy and entropy changes that determines the sign of ∆G. That being said, any spontaneous process must ultimately have a ∆Stotal that is positive when considering both the system and its surroundings.
For example, an enthalpically favored reaction may have a negative ∆S (entropy decrease), but if the enthalpy decrease (∆H negative) is sufficient, it can still result in a negative ∆G and be spontaneous. Conversely, an entropically favored reaction might have a positive ∆S that contributes enough to overcome a positive ∆H, particularly at higher temperatures, making the reaction spontaneous. Ultimately, it is important to analyze both enthalpy and entropy changes when determining the feasibility of chemical reactions.