⚖️ Equilibrium Constant (Kc) & ICE Calculator
Set the reaction coefficients, initial concentrations and Kc to find the equilibrium concentrations and which way the reaction shifts.
Reaction: aA + bB ⇌ cC + dD — set coefficients (0 to drop a species) and initial concentrations.
| Species | Coefficient | Initial conc. (M) |
|---|---|---|
| A (reactant) | ||
| B (reactant) | ||
| C (product) | ||
| D (product) |
Equilibrium concentrations
Q₀ = 0.00e+0 · shifts forward[A]
0.2205
[B]
0.2205
[C]
1.559
Extent of reaction ξ = 0.7795 M
Builds the ICE table and solves for the extent of reaction ξ where the reaction quotient Q equals Kc: [reactant] = initial − coeff·ξ, [product] = initial + coeff·ξ. Comparing the initial Q₀ to Kc gives the shift direction (Q < K → forward, Q > K → reverse). Concentrations are molar; assumes all species are aqueous/gas-phase and included in Q. 🔒 In your browser.
How the equilibrium constant (kc) & ice calculator works
Given a reaction aA + bB ⇌ cC + dD, its initial concentrations and the equilibrium constant Kc, the tool builds the ICE table and finds the extent of reaction ξ at which the reaction quotient Q equals Kc: each concentration becomes initial ± coefficient·ξ. It solves that numerically (Q is monotonic in ξ), and compares the initial Q₀ with Kc to tell you whether the reaction shifts forward or reverse to reach equilibrium.
Include only species that appear in the equilibrium expression — leave out pure solids and liquids (set their coefficient to 0). Concentrations are molar; for gas-phase equilibria you can use Kc with molar concentrations. The solver assumes a single reaction reaching one equilibrium state within the physically allowed range of ξ.
Frequently asked questions
How do I find equilibrium concentrations from Kc?
Set up an ICE table: each species changes by its coefficient times the extent of reaction ξ. Then solve Q(ξ) = Kc for ξ and substitute back. The tool does this numerically for you and reports every equilibrium concentration.
What is the reaction quotient Q?
The same expression as Kc but evaluated at the current (initial) concentrations. Comparing them predicts the shift: Q < Kc shifts forward (toward products), Q > Kc shifts reverse (toward reactants), and Q = Kc means the system is already at equilibrium.
What is an ICE table?
A bookkeeping table of Initial, Change and Equilibrium concentrations. The Change row is the coefficient times the extent of reaction ξ (negative for reactants, positive for products); the Equilibrium row feeds into the Kc expression.
Which species do I include?
Only gases and aqueous species — the ones that appear in the equilibrium-constant expression. Pure solids and pure liquids have an activity of 1 and are left out (set their coefficient to 0).
What does the extent of reaction ξ mean?
How far the reaction proceeds from the initial state to equilibrium, in mol/L. A positive ξ means net forward reaction; negative means net reverse. Each concentration shifts by its coefficient times ξ.