The
free energy change for a reaction depends on the r
eactants and products, not on the
pathway between them.
Thus the
free energy change for a reaction (1) may be calculated from the
free energy changes for reactions that
can be
combined to give reaction (1).
This is done by combining the free energies of the contributing reactions in the same way as the equation for the reactions were combined.
The
direction of spontaneous change (if any) for reaction (1) can be deduced from the sign of the free energy change.
- If ΔG is negative, the process is spontaneous in the forward direction. Reaction occurs until equilibrium is reached.
- If ΔG is zero, the system is at equilibrium, and there is no tendency for the composition of the mixture to change.
- If ΔG is positive, the process is spontaneous in the reverse direction. Reaction occurs until equilibrium is reached.