Chemical Equilibrium Calculator
Set up an ICE table and solve for equilibrium concentrations from Kc and initial concentrations. Shows Q, the quadratic and a check of Kc.
What this calculator does
Enter Kc, the coefficients and the starting concentrations. The calculator writes the equilibrium expression, finds Q, solves the ICE table for x and checks that the answer reproduces Kc.
When you need it
Equilibrium calculations decide how far a reaction goes. They are used for solubility, acid-base chemistry, buffers and industrial processes such as ammonia synthesis.
Formulas
- Kc = [C]ᶜ[D]ᵈ ÷ ([A]ᵃ[B]ᵇ)
- Q has the same form as Kc but uses the concentrations at the start
- Q < Kc: the reaction moves forward; Q > Kc: it moves back
How to use it
- Write the balanced equation and enter the coefficients.
- Enter Kc and the initial concentrations (use 0 for products at the start).
- Read Q, the equilibrium concentrations and the check that gives Kc back.
Worked example
For A ⇌ B + C with Kc = 1.8 × 10⁻⁵ and [A]₀ = 0.10 M (no B or C at the start), find the equilibrium concentrations.
- ICE table: [A] = 0.10 − x, [B] = x, [C] = x
- Kc = x² ÷ (0.10 − x) = 1.8 × 10⁻⁵
- Solving the quadratic gives x = 1.33 × 10⁻³ M
Answer
[B] = [C] = 1.33 × 10⁻³ M and [A] = 0.0987 M.
Common mistakes
- Including solids and pure liquids in the equilibrium expression.
- Using the approximation 0.10 − x ≈ 0.10 when x is not small enough.
- Mixing up Q and Kc when deciding which way the reaction shifts.
Related tools
Frequently asked questions
What is an ICE table?
A table of Initial, Change and Equilibrium concentrations. It turns an equilibrium problem into one equation for x.
What does a large Kc mean?
Kc much larger than 1 means products are favoured at equilibrium; much smaller than 1 means reactants are favoured.
What is the reaction quotient Q?
Q is calculated like Kc but with the concentrations at any moment. Comparing Q with Kc shows which way the reaction will move.