Physical significance of magnitude of ΔG (change in Gibbs free energy) of a reaction [closed]








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In thermodynamics, we know that if $\Delta G$ of a reaction is negative, the reaction is spontaneous.


Suppose we are given with two spontaneous reactions ($\Delta G\lt0$) with corresponding magnitudes of $\Delta G$. Can we extract any other information from these magnitudes?




It is only a rule of thumb that a negative value for $\Delta G^0$ of a reaction means that a reaction is spontaneous. If you start out with pure reactants (and no products present), all reactions are spontaneous, irrespective of the $\Delta G^0$. A negative value for $\Delta G^0$ only signifies that the equilibrium constant is greater than 1. 


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The change in the Gibbs free energy for a process at a constant temp. and pressure is equal to how much non-expansion work it can do.


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