Equilibrium constant converter
Convert an equilibrium constant into the free energy behind it, and into how far the reaction actually goes.
That's about the same as a favorable reaction. At equilibrium about 99.9% has reacted.
What it means
Which way does it go?
Values are at 25 °C. Free energy scales with temperature, so the same K means a different ΔG° in a furnace.
Every unit
Your equilibrium in every unit
Learn
Three things worth knowing
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5.7 kJ/mol is a factor of ten
At 25 °C, ΔG° = −5.71 × log₁₀K. So −11.4 kJ/mol means K = 100, and −34 means a million.
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Why the logarithm
Free energy is additive when reactions are added; equilibrium constants multiply. The logarithm is what converts one into the other.
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K says where, not how fast
Diamond turning to graphite has a favorable K and takes longer than the age of the universe. Thermodynamics sets the destination; kinetics sets the speed.
Shortcuts
Popular equilibrium conversions
Background
About K and ΔG°
The equilibrium constant and the free energy change are the same statement twice: ΔG° = −RT ln K. A K of 1,000 is −17 kJ/mol, and a K of 1 is exactly zero.
The logarithm is steep: every 5.7 kJ/mol of free energy is a factor of ten in K, so small energy differences decide reactions completely.