In fact, the possibilities can be roughly divided into four parts:

: ΔG^o < -60 kJ: reaction "complete"; -60 kJ < ΔG^o < 0 kJ: mostly products; 0 kJ < ΔG^o < +60 kJ: mostly reactants; ΔG^o > +60 kJ: "no" reaction

These various cases imply that chemical processes are reversible and that is theoretically true. In practice, many are not. The manipulation of the extent of reaction or making a non-spontaneous process happen can be visualized as four scenarios based on the Gibbs-Helmholtz relationship. These ideas can be applied to reactions on the industrial scale (the cement again...) as well as to mundane matter such as when water will boil.

So free energy finally gives us a tool for predicting whether a reaction will occur or not under specific conditions. Or does it?