Chemistry
Equilibrium Constant (Kc) Calculator
Calculate Kc for aA + bB ⇌ cC + dD from the equilibrium concentrations.
Your inputs
Change any value to update the result instantly.
Equilibrium constant Kc
0.64
Product side term
0.04
Reactant side term
0.0625
Change in moles (Δn)
-2
Reading
Reactants are favoured at equilibrium
Pure solids and pure liquids are left out of the expression — set their coefficient to 0. Kc is defined rigorously with activities, so it is strictly unitless.
What this calculator does
Calculates the concentration equilibrium constant Kc from equilibrium concentrations and the balanced coefficients.
What your result means
Kc above 1 means products dominate at equilibrium; Kc below 1 means reactants dominate.
Formula and working
Kc = ([C]^c × [D]^d) ÷ ([A]^a × [B]^b)
- 1
Collect the inputs
[A] at equilibrium = 0.5 mol/L; Coefficient a = 1; [B] at equilibrium = 0.5 mol/L; Coefficient b = 3; [C] at equilibrium = 0.2 mol/L; Coefficient c = 2; [D] at equilibrium (use 0 if absent) = 0 mol/L; Coefficient d = 0
- 2
Apply the formula
Kc = ([C]^c × [D]^d) ÷ ([A]^a × [B]^b)
- 3
Result
Equilibrium constant Kc = 0.64
Frequently asked questions
Symbols and assumptions
- Kc
- Equilibrium constant in concentration terms
- a, b, c, d
- Balanced coefficients
- [X]
- Equilibrium concentration in mol/L
- • The concentrations entered are equilibrium values, not starting values.
- • Pure solids and pure liquids are excluded by setting their coefficient to zero.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • Kc is rigorously defined with activities, so it is strictly unitless. It changes with temperature but not with concentration.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
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