ΔGº and ΔG

[mikaela 3F]

Can someone explain the difference between ΔGº and ΔG when it comes to being positive/negative/zero? Why does ΔGº indicate what side the equilibrium favors while ΔG indicates spontaneity?

[Ishita S 2E]

DeltaG values can be positive or negative, with a negative DeltaG indicating a spontaneous reaction and a positive DeltaG indicating a non-spontaneous. Delta G typically is used to calculate delta H and thus the -Tdelta S in nonstandard conditions (most conditions). However, delta g naught is used for very precise standard conditions where it’s constant and in the form for calculating delta g in the equation delta g= delta naught + rt ln Q

[Jasmin Gonzalez]

ΔGº represents the standard Gibbs free energy change of a reaction at equilibrium, with a negative value that indicates a forward-favoring equilibrium while positive values indicate a reverse-favoring equilibrium and zero indicates equilibrium. ΔG is Gibbs free energy change under non-standard conditions that determine the spontaneity of a reaction. So negative ΔG is spontaneous reactions positive is non-spontaneous reaction and zero is equilibrium

[606158388]

The difference between ΔGº and ΔG is that the standard value is constant because it is the free energy when the reactants are at their standard values. The non-standard value is at any reagent composition meaning that the non standard value changes as the reaction progresses. If the standard value is negative, the equilibrium lies on the products side. If the standard value is positive, the equilibrium lies on the reactant side. The nonstandard value indicates spontaneity at a certain composition of reactant and product.

[Stephanie_manasyan]

Hi! ΔG∘′ describes the reaction at equilibrium, while ΔG describes the actual energy being exchanged at any point in a reaction. ΔG°' is the standard Gibbs free energy change under physiological conditions, which means that the pH of the solution is 7. Hope this helps.