Free Energy and Equilibrium

Kinetics decide if a process will go fast or slow to the
equillbrium position. Equilibrium from the thermodynamics
view is the point at the lowest value of free energy available to
the reacton system. When substances undergo a chemical
reaction the equilibrium is reached when the free energy is at a
minimum. This point is where G_{products} = G_{reactants}
or when

G = G_{products} - G_{reactants} = 0

From the equation G = G° + RT ln (Q) and at equilibrium G equals 0 and Q equals K.

Then G = 0 = G° + RT ln (K)

or G° = -RT ln (K)

Qualitative Relationship between the Change in Standard Free Energy and the Equilibrium Constant for a Given Reacton

G° | K |

G° = 0 | K = 1 |

G° < 0 | K > 1 |

G° > 0 | K < 1 |