Final answer:
The change in free energy (ΔG) indicates a reaction's spontaneity, equilibrium position, and the maximum useful work obtainable from it.
Step-by-step explanation:
Knowing the change in free energy ( ΔG ) of a reaction tells us whether the reaction is spontaneous, its equilibrium position, and the amount of useful work that can be extracted from the reaction. The sign of ΔG indicates the direction of spontaneity: a negative value means the reaction will proceed spontaneously, while a positive value indicates that the reaction is not spontaneous as written (but may proceed spontaneously in the reverse direction). The magnitude of ΔG at constant temperature and pressure equals the maximum work a system can perform on its surroundings during a spontaneous process. The standard free energy change (ΔG°) of a reaction, calculated from the standard free energies of formation (ΔG°f) for reactants and products, informs about the thermodynamic favorability under standard conditions.