Delta G standard equals minus RT ln K linking thermodynamics with equilibrium constants.
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The standard Gibbs energy change is directly related to the equilibrium constant through delta G standard equals minus R times T times the natural logarithm of K, where R is the gas constant. A large negative delta G standard gives a large K, meaning the equilibrium mixture contains mostly products, while a positive value gives K less than one and favors reactants. A value of zero corresponds to K equal to one, where products and reactants are present in comparable amounts. This relation connects tabulated thermodynamic data with equilibrium composition, allowing K to be computed without direct measurement. It is one of the central links between thermodynamics and chemical equilibrium.
Key ideas: Use K equals exp of minus delta G degree divided by RT. Each 5.7 kJ per mole of delta G degree changes K by about a factor of ten at 298 K. When delta G degree is more negative than about minus 30 kJ per mole, the reaction goes essentially to completion.
Common mistakes and connections: Do not mix up delta G degree with delta G, since only delta G equals zero at equilibrium. Another error is to forget that K for gases uses pressures or concentrations according to the definition. This relation unites thermodynamics with equilibrium and underlies the van't Hoff equation.
A large equilibrium constant corresponds to a negative standard delta G (delta G = -RT ln K): the reaction proceeds far toward products before equilibrium is reached. The interactive lesson shows this as a live animation or chart.
If delta G standard is -5.7 kJ per mole at 298 K, then K is about 10, since ln K equals 5700 divided by (8.314 times 298).
Delta G standard equals minus RT ln K linking thermodynamics with equilibrium constants.
Free Energy and Equilibrium is a advanced topic in Thermodynamics & Energetics. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Thermodynamics & Energetics first: Gibbs Energy and Spontaneity, Temperature Dependence of Spontaneity, Standard Free Energy of Formation.
The next topics in Thermodynamics & Energetics are Reaction Quotient and Free Energy and Free Energy and Work.
Yes. The interactive lesson includes a self-check question on Free Energy and Equilibrium, and the Thermodynamics & Energetics quiz draws on every topic in this area.
Free Energy and Equilibrium is topic 41 of 91 in Thermodynamics & Energetics.