How to use this calculator
- Enter a balanced or unbalanced reaction with a phase for each species.
- Enter one positive activity for each included gas or aqueous species.
- Calculate and review the generated equilibrium expression.
Formula and variables
K = product activities^coefficients / reactant activities^coefficients
| Symbol | Meaning | Unit |
|---|---|---|
| K | equilibrium constant | activity-based |
| nu | stoichiometric coefficient | power |
Worked example
For N2(g) + 3 H2(g) ⇌ 2 NH3(g), the expression is [NH3]^2 / ([N2][H2]^3).
Interpretation
Pure solids and liquids are excluded only when their phases are explicitly declared; gases and aqueous species remain.
Common mistakes
- Declare a phase for every equilibrium species.
- Activities and partial-pressure or concentration approximations must be positive.
Frequently asked questions
Which species are excluded from K?
The calculator excludes pure solids and pure liquids when their phases are stated.
Can I enter concentrations as activities?
Yes, as an explicit ideal-solution approximation. Use dimensionless activities for rigorous work.
Does the calculator use balanced coefficients as powers?
Yes. It balances the reaction first and uses the exact coefficients in the expression.
Can I use scientific notation?
Yes. Enter values such as 6.022e23 or 1.0e-6 in a numeric field.
How should I round the result?
Keep extra digits during the calculation. Round the final result to the precision required by your data.