Equilibrium Constant Calculator
Calculate equilibrium constants (Kc or Kp) from equilibrium concentrations or partial pressures, convert between Kc and Kp, and determine the standard Gibbs free energy change (ΔG°). Supports reactions with up to 2 products and 2 reactants.
The equilibrium constant quantifies the position of a chemical equilibrium. For a generic reaction aA + bB ⇌ cC + dD, the equilibrium constant Kc is defined as [C]^c[D]^d / [A]^a[B]^b, where brackets denote molar concentrations at equilibrium.
Key Relationships
- Kc uses molar concentrations (mol/L). Kp uses partial pressures (atm) for gas-phase reactions.
- Conversion: Kp = Kc(RT)^Δn, where R = 0.08206 L·atm/(mol·K) and Δn is the change in moles of gas (products minus reactants).
- Gibbs Free Energy: ΔG° = -RT·ln(K), where R = 8.314 J/(mol·K). A large K (>> 1) means products are favored and ΔG° is negative (spontaneous). A small K (<< 1) means reactants are favored.
Interpreting K Values
K >> 1: Equilibrium lies far to the right (product-favored). K << 1: Equilibrium lies far to the left (reactant-favored). K ≈ 1: Significant amounts of both reactants and products are present at equilibrium. Temperature changes shift K according to the van't Hoff equation.