When is gibbs free energy equal to zero

Because at equilibrium, everything that G depends on is constant. Related questions Can gibbs free energy be negative? How do enzymes affect gibbs free energy? How is Gibbs Free Energy calculated? How is gibbs free energy related to enthalpy and entropy? Why does gibbs free energy decrease with temperature? Why is Gibbs free energy important? For a system at constant temperature and pressure, we can summarize the following results:. If the conversion of liquid water to water vapor is carried out at 1 atm and the normal boiling point of The energy required for vaporization offsets the increase in entropy of the system.

We can also calculate the temperature at which liquid water is in equilibrium with water vapor. At temperatures greater than Below Instead, water vapor at a temperature less than A similar situation arises in the conversion of liquid egg white to a solid when an egg is boiled. The major component of egg white is a protein called albumin, which is held in a compact, ordered structure by a large number of hydrogen bonds.

Consider the following possible states for two different types of molecules with some attractive force:. There would appear to be greater entropy on the left state 1 than on the right state 2.

Thus the entropic change for the reaction as written i. To go to the left, we have to overcome this attractive force input heat energy and the left direction is unfavorable with regard to heat energy q. This reaction as written, is therefore, enthalpically favorable and entropically unfavorable. Hence, It is enthalpically driven. Looking at the same process from an opposite direction:. This reaction as written, is entropically favorable , and enthalpically unfavorable; it is entropically driven.

The change in Gibbs energy is equal to the maximum amount of work that a system can perform on the surroundings while undergoing a spontaneous change at constant temperature and pressure :. We can rearrange this equation as follows:. This path might involve the use of constant temperature reservoirs, small weights to be added or removed from a piston, and semipermeable membranes. This means the free energy will keep on reducing until no more reduction is possible.

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Create a free Team What is Teams? Learn more. Gibbs free energy-minimum or zero? Ask Question. Asked 9 years, 6 months ago. Active 1 year, 1 month ago. Viewed 27k times. What am I missing here? Improve this question. ManishEarth ManishEarth Add a comment. Active Oldest Votes. Improve this answer. F'x F'x But doesn't a system go towards the lesser G? If G is nonzero elsewhere, this means that it had to increase at one point.