Equilibrium Constant Calculator

Equilibrium Constant Calculator

The Equilibrium Constant Calculator computes $K$ for a reversible reaction from equilibrium concentrations and stoichiometric coefficients. For a general reaction $a\text{[A]} + b\text{[B]} \rightleftharpoons c\text{[C]} + d\text{[D]}$:

$$K = \frac{[\text{C}]^c \times [\text{D}]^d}{[\text{A}]^a \times [\text{B}]^b}$$

Concentrations are molarity (mol/L). When $K > 1$, products are favored at equilibrium. When $K < 1$, reactants are favored. When $K = 1$, both sides are comparable.

Example: for $2\,\text{SO}_2 + \text{O}_2 \rightleftharpoons 2\,\text{SO}_3$ with $[\text{SO}_2] = 0.03$, $[\text{O}_2] = 0.035$, and $[\text{SO}_3] = 0.5$ mol/L:

$$K = \frac{0.5^2}{0.03^2 \times 0.035} \approx 7.94 \times 10^3$$

Related tools: Chemical Entropy Calculator and Concentration Calculator.