ICE Table Equilibrium Calculator
Equilibrium concentrations for A ⇌ B + C (or A ⇌ 2B, A + B ⇌ C…) from K and initial concentrations — the ICE table filled in, the exact quadratic solution, extent of reaction and a check of the 5% approximation.
How it works
Set up Initial / Change (±x by stoichiometry) / Equilibrium rows, write K in terms of x and solve; e.g. A ⇌ B + C: K = (b₀+x)(c₀+x) ÷ (a₀ − x)
The ICE table is the bookkeeping that turns an equilibrium constant into actual concentrations: list what you start with, express every change in terms of one unknown x using the stoichiometric coefficients, substitute into K and solve. The result is a quadratic (or worse) that this calculator solves numerically on the physically meaningful interval, so you get the right root without the algebra. The 5% rule tells you when the shortcut of ignoring x against the initial concentration would have been acceptable.
Worked example
PCl₅ ⇌ PCl₃ + Cl₂ with K = 0.0416 and 0.5 M PCl₅: x²/(0.5 − x) = 0.0416 → x = 0.125 M, so 25% dissociates — far too much for the 5% approximation.
Frequently asked questions
Why can x be negative?
If products are present in excess (Q > K) the reaction runs backwards; x is then negative and the table still works.
What about gases with Kp?
Use partial pressures in the table instead of concentrations — the algebra is identical.
Related calculators
For study and planning — check units and conditions against your data source before using a result in the lab.