ChemBench

Equilibrium Constant Calculator

The bridge between thermodynamics and equilibrium — how energy determines where a reaction settles.

ΔG° (standard Gibbs energy)

Temperature

Equilibrium constant K

7.524

What you entered

ΔG° (standard Gibbs energy): -5000Temperature: 298

1
−ΔG° ÷ RT
−(-5000) ÷ (8.314 × 298)= 2.0181
2
K = e^(−ΔG°/RT)
e^(2.0181)= 7.5241

Result

Equilibrium constant K: 7.524

With ΔG° = -5000 J/mol at 298 K, the equilibrium constant K = 7.524. Products are favored at equilibrium.

Equilibrium constant from Gibbs free energy

K is the exponential of minus delta G over RT. A negative delta G gives K greater than 1, meaning products are favoured at equilibrium.

Delta G	Temperature	K	Favours
-50 kJ/mol	298.15 K	5.7558 x 10^8	Products strongly
-10 kJ/mol	298.15 K	5.6497 x 10^1	Products
-10 kJ/mol	500 K	1.1085 x 10^1	Products, less so when hot
0 kJ/mol	298.15 K	1.0000	Neither
+10 kJ/mol	298.15 K	1.7700 x 10^-2	Reactants
+20 kJ/mol	298.15 K	3.1330 x 10^-4	Reactants strongly

The relationship is exponential, so small energy changes move K enormously: 10 kJ/mol either side of zero spans four orders of magnitude in K.

ΔG° tells you which side wins

A large negative ΔG° gives a large K (products favored), while a large positive ΔG° gives a tiny K (reactants favored). At ΔG° = 0, K = 1 and neither side is favored — the relationship ΔG° = −RT ln K quantifies exactly how strongly a reaction favors products or reactants.

Temperature shifts the equilibrium

Even with the same ΔG°, changing temperature changes K because of the RT factor — this is the mathematical basis of Le Chatelier's principle for temperature changes, and it's why some reactions that are unfavorable at room temperature become favorable at high temperatures.

Frequently asked questions

ΔG° is -30 kJ/mol at 298 K — what is K?

K = exp(-ΔG°/RT) = exp(30000/(8.314×298)) = exp(12.1) ≈ 1.8 × 10⁵. Products are strongly favored.

How is the equilibrium constant related to the Gibbs free energy calculator?

They are two views of the same relationship: ΔG° = -RT ln K. The Gibbs calculator finds ΔG from ΔH and ΔS; this calculator converts that ΔG into K, telling you the product-to-reactant ratio at equilibrium.

Does K change with concentration?

No. K depends only on temperature for a given reaction. Changing concentrations shifts Q (the reaction quotient), driving the system toward or away from equilibrium, but K itself stays fixed at a given temperature.

What does K = 1 mean?

At equilibrium, products and reactants are present in comparable amounts. K >> 1 means products dominate; K << 1 means reactants dominate. K = 1 is the thermodynamic tipping point where ΔG° = 0.