Chemical Equilibrium Calculator
Solve an ICE table exactly for three simple reaction types — dissociation (A ⇌ B + C, such as a weak acid), isomerization (A ⇌ B) and association (A + B ⇌ C) — from the initial concentration and Kc.
Last updated: September 2026
Formula below · 2 sources (pubchem.ncbi.nlm.nih.gov, Wikipedia) · Updated Sep 2026
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About this calculator
The ICE (Initial, Change, Equilibrium) table tracks how concentrations shift from initial conditions to equilibrium. Let x be the equilibrium concentration of product formed from an initial concentration C₀ (no product present at the start). Dissociation A ⇌ B + C: Kc = x² / (C₀ − x), so x = (−Kc + √(Kc² + 4·Kc·C₀)) / 2 — for a weak acid HA this x is [H⁺] (the familiar √(Ka·C₀) is its small-K limit). Isomerization A ⇌ B: Kc = x / (C₀ − x), so x = C₀·Kc / (1 + Kc). Association A + B ⇌ C with [A]₀ = [B]₀ = C₀: Kc = x / (C₀ − x)², so x = [(2KcC₀ + 1) − √(4KcC₀ + 1)] / (2Kc). The calculator solves these quadratics exactly (in a numerically stable rearranged form), so it stays accurate for any Kc, large or small. Kc must be the concentration-based constant for the reaction exactly as written; temperature affects Kc through the van't Hoff equation.
How to use
Example 1 — Weak acid. 0.50 M acetic acid, Ka = 1.8 × 10⁻⁵, reaction type = Dissociation. x = (−1.8×10⁻⁵ + √((1.8×10⁻⁵)² + 4 × 1.8×10⁻⁵ × 0.50)) / 2 = 0.0029911 M, so [H⁺] ≈ 0.0030 M (pH 2.52) and only 0.6% of the acid has dissociated. (The site rounds results to two decimals above 0.005, so read small results with that in mind.) Example 2 — Isomerization. [A]₀ = 0.50 M, Kc = 4.0, reaction type = Isomerization: x = 0.50 × 4.0 / (1 + 4.0) = 0.40 M of B, leaving 0.10 M of A (ratio 4.0 = Kc, as required). Example 3 — Same numbers as Dissociation: x = (−4 + √(16 + 8)) / 2 = 0.4495 M, so [A] = 0.0505 M and Kc = 0.4495² / 0.0505 = 4.0. ✓
Frequently asked questions
How do I set up an ICE table for a chemical equilibrium problem?
An ICE table has three rows — Initial, Change, and Equilibrium — and one column per species in the reaction. Write the initial concentrations in the first row (often 0 for pure products). In the Change row, express shifts in terms of a variable x, with reactants losing x (times stoichiometric coefficient) and products gaining x. The Equilibrium row is Initial + Change. Substitute the equilibrium row expressions into the Kc expression and solve for x to find all equilibrium concentrations.
What does a large equilibrium constant Kc mean for a chemical reaction?
A large Kc (much greater than 1) means the reaction strongly favors products at equilibrium — nearly all reactants are converted. A small Kc (much less than 1) means the equilibrium lies to the left and only tiny amounts of product form. How much converts at a given Kc also depends on the reaction type and concentration: for a dissociation, dilution increases the fraction converted, while for an association it decreases it. Kc is temperature-dependent: for exothermic reactions, raising temperature decreases Kc, shifting equilibrium back toward reactants, as described by Le Chatelier's principle.
Why does temperature affect the equilibrium constant in chemical reactions?
The equilibrium constant Kc is related to the standard Gibbs free energy change by ΔG° = −RT ln Kc, and ΔG° itself depends on temperature through ΔG° = ΔH° − TΔS°. As temperature changes, ΔG° changes, so Kc changes. For endothermic reactions (ΔH° > 0), increasing temperature raises Kc and favors products. For exothermic reactions (ΔH° < 0), increasing temperature lowers Kc and favors reactants. This is the thermodynamic basis of Le Chatelier's principle and is quantified by the van't Hoff equation.