Equilibrium Constant Calculator

Calculate Equilibrium Constants and Reaction Quotients

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Concentration Equilibrium Constant (Kc) Calculator

Calculate Kc from equilibrium concentrations.

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Pressure Equilibrium Constant (Kp) Calculator

Calculate Kp from partial pressures.

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Reaction Quotient (Q) Calculator

Calculate Q and compare with K to determine reaction direction.

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Understanding Equilibrium Constants

What are K and Q?

For a reaction aA + bB ⇌ cC + dD:

Kc = [C]ᶜ[D]ᵈ/[A]ᵃ[B]ᵇ

Kp = (Pᶜ₍C₎Pᵈ₍D₎)/(Pᵃ₍A₎Pᵇ₍B₎)

Kp = Kc(RT)ᐩⁿ

Interpretation

Comparing Q and K:

  • Q < K: Forward reaction
  • Q = K: Equilibrium
  • Q > K: Reverse reaction
  • K > 1: Products favored

Applications

Used to determine:

  • Reaction direction
  • Product yield
  • Equilibrium position
  • Reaction spontaneity

Common Values

Typical K values:

  • Strong acid: K > 1
  • Weak acid: K < 1
  • Water: Kw = 1×10⁻¹⁴
  • Complete reaction: K > 10³