How to use (3 steps)
- Enter up to four species with their roles (reactant/product), stoichiometric coefficients, and initial concentrations or partial pressures.
- Select Kc or Kp, enter the equilibrium constant, and optionally toggle the small-x approximation check.
- Compute to generate the ICE table, reaction extent x, and a step-by-step log. Copy the URL to share the exact setup.
The default example auto-loads N2O4 <=> 2NO2 at 25 °C, showing a modest forward shift. All calculations run in your browser only.
Reaction and initial conditions
Enable at least one reactant and one product. Units update automatically when you switch Kc ↔ Kp.
| Include | Species | Role | Coefficient | Initial |
|---|---|---|---|---|
Equilibrium constant and options
Use mol/L for Kc and bar for Kp.
Enter K at the temperature of interest. Temperature dependence is not modeled in this version.
Summary
How it's calculated
How to use this calculator effectively
Start by balancing one equilibrium expression, confirm whether your constant is Kc or Kp, then enter only the species that actually appear in that expression. Use the first run as a baseline, then change one concentration or coefficient at a time so you can see which assumption changes the equilibrium shift.
FAQ
What kinds of reactions can I solve with this tool?
It handles a single equilibrium reaction with up to four species, using Kc for solution equilibria or Kp for gas-phase equilibria. Multi-step or coupled equilibria are out of scope.
Why do I see errors about negative concentrations or no physical solution?
Some K values and initial conditions produce no non-negative equilibrium concentrations in the feasible interval, or the numeric solver may not find a root when the change is extreme. Adjust the starting concentrations or K and try again.
What is the 5% small-x approximation?
When the reaction extent x is small compared with initial concentrations, you can assume C0 ± x ≈ C0 to simplify algebra. This tool reports the maximum relative change and flags whether the 5% rule is satisfied.
What should I enter first?
Start with the minimum required inputs shown above the calculate button, then keep optional settings at their defaults for a first run. After you get a baseline result, change one parameter at a time so you can see exactly what caused the output to move.
How precise are the results?
The calculator keeps internal precision and rounds only for display. Small differences can still appear when another tool uses different constants, unit assumptions, or rounding rules. Match the same assumptions before comparing values.
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