Enter equilibrium molar concentrations and balanced-reaction coefficients for any number of dissolved or gaseous species. Omit pure solids and liquids. The calculator estimates the concentration-based equilibrium constant at the composition’s temperature.

One species per line: coefficient, equilibrium concentration. For example: 2, 0.15. Use the balanced reaction; omit pure solids and liquids.

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Equilibrium Constant Formula

For the balanced reaction aA + bB ⇌ cC + dD, the following concentration expression uses equilibrium concentrations in mol/L. Pure solids and liquids are omitted. Concentrations normalized by the 1 mol/L standard state give a dimensionless ideal approximation; thermodynamic constants use activities.

K = ([C]c × [D]d) / ([B]b × [A]a)
  • Where K is the equilibrium constant
  • [A,B,C,D] are the molar concentrations of those substances
  • a,b,c,d are the coefficients of each substance

To calculate the equilibrium constant, take each molar concentration and raise it to the power of the coefficient of each substance. Next, multiply the results from C and D together and divide by the product of the results from B and A.

Equilibrium Constant Definition

An equilibrium constant relates product and reactant activities at equilibrium for a specified reaction and temperature.

Equilibrium Constant Example

How to calculate equilibrium constant?

  1. First, determine the molar concentrations of each substance

    Calculate or measure the concentrations of each individual substance.

  2. Next, determine the coefficients

    Determine the corresponding coefficients of each substance.

  3. Calculate the equilibrium constant

    Using the information from steps 1 and 2, calculate the equilibrium constant.

FAQ

What is an equilibrium constant?

An equilibrium constant relates product and reactant activities at equilibrium for a specified reaction and temperature.