Equilibrium Constant Calculator

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Kc uses molar concentrations; Kp uses partial pressures in atm. Choose "Solve for product C" to find an unknown concentration given K.
Equilibrium molar concentration (Kc mode) or partial pressure in atm (Kp mode) of product C.
mol/L
Stoichiometric coefficient of C in the balanced equation.
Leave blank or set coefficient to 0 if there is no second product.
mol/L
Set to 0 if there is no second product.
Equilibrium concentration or partial pressure of reactant A.
mol/L
Stoichiometric coefficient of A in the balanced equation.
Equilibrium concentration or partial pressure of reactant B. Set coefficient to 0 if absent.
mol/L
Set to 0 if there is no second reactant.
Temperature is needed for Kp conversion (Kp = Kc(RT)^delta-n) and Gibbs free energy (delta-G = -RT ln K). 298 K = 25 C.
Equilibrium constant (Kc)Comparable amounts at equilibrium
2.5
Kc (decimal)2.5
log₁₀ Kc0.398
Kp from concentrations61.13
Kp (decimal)61.132465
Δn (gas moles change)1
ΔG° (standard Gibbs free energy)-2.27kJ/mol
Kc (value)2.5
Kp (value)61.132465

K = 2.5 for the values you entered.

  • K is dimensionless: each concentration (or pressure) is referenced to a standard state of 1 mol/L (or 1 atm).
  • Because K is greater than 1, the numerator (products) dominates, so the forward reaction has gone further than the reverse, products are favoured at equilibrium.
  • K depends only on temperature; changing concentrations shifts the equilibrium position but leaves K unchanged.
  • The equivalent Kp at 298 K is approximately 61.13.

Next stepSwitch to "Convert Kc to Kp" mode to get the gas-phase equilibrium constant, or to "Gibbs free energy" to find delta G.

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