Negative entropy change implies positive Gibbs free energy change if the enthapy variation would be zero, under isothermal and isobaric conditions:. DelG = Del H- T Del S (for solid state reactions delH about EQ delU )

What do you mean by'' the change in the gibbs free energy was nearly the same''?

• Proposed reaction can proceed along the direction one assumes if the change in the Gibbs free energy would be negative otherwise inverse reaction takes place under isothermal isobaric conditions.
• İf the Gibbs free energy change would be negative with an amount almost equal to the change in the entropic contribution that means enthalpy of the reaction is endothermic and its magnitude almost twice as much compared to the entropic contribution. Abs Del H EG Abs (2T Del S)

Thanks for the reply

The Gibbs energy change is delta G = delta (H of system) - T(delta S of system) = -T(delta S of surroundings) -T(delta S of system) = -T(TOTAL delta S). An activated complex always corresponds to a lower TOTAL entropy than either the reactants or the products. Otherwise it would not be an activated-complex state; otherwise there would be no barrier to the occurrence of the reaction in either the forward or reverse direction. If the entropy of the system in the activated-complex state is lower than in the reactant state but the Gibbs energy of the system is about the same in the activated-complex state as in the reactant state, then the entropy of the surroundings must be higher when the system is in the activated-complex state than in the reactant state. But it must be higher to a lesser degree than that of the system is lower if the TOTAL entropy is to be lower in the activated-complex state, i.e., if the activated-complex state is to exist at all. Under any circumstances it is the TOTAL reduction of entropy in entropy TOTAL activation delta S from the reactant state to the activated-complex state that is important. At constant pressure TOTAL activation delta S = (activation delta G)/T, at constant volume TOTAL activation delta S = (activation delta G)/T. (The Gibbs energy G assumes constant temperature and pressure; for reactions at constant temperature and volume, use the Helmholtz free energy A instead.)

One shouldn't forget the concept of activated complex is artificİally introduced notion in Reaction Knetics, which doesn't have any counter part in thermodynamics whether it irreversible or not. Thermodynamics worries about only the initial and final states, and tells us that whether a given reaction along the proposed direction is plausible or not ( in forward or backward ) under given constrains regardless its path. That means it can't ensure us that the reaction really takes place in nature. İf this an isochoric reaction that takes place under constant temperature and volume one has to look at the difference between Helmholtz free energies associated with the initial and final states ' . İn the case of isobaric and isothermal conditions, Gibbs free difference plays the major role. Therefore Classical thermodynamics alone can' t handle our kinetics problems whatsoever because it doesn^t tells us that how system can over come higher free energy barriers duıring the reaction path and/or the selection of the optimal path. Entropy is a bad choice here, and what type of entropy, internal or external or bulk and surface etc. Choice of charactrestic function (U,S, H, F, G) depends on the applied constrains (T, V, P etc),and dependence is also not arbitrary .

Entropy: A concept that is not a physical quantity

https://www.researchgate.net/publication/230554936_Entropy_A_concept_that_is_not_a_physical_quantity