Equilibrium Constant Calculator

Calculate Kc, Kp, Ka, Kb equilibrium constants, solve ICE tables, and perform pH calculations from dissociation constants.

Kc (Concentration Equilibrium Constant)

Supports: ⇌, <=>, <-->, ==, or = • Auto-parses coefficients from equation
Equilibrium Concentrations (M)
Haber Process H₂ + I₂ ⇌ HI N₂O₄ ⇌ NO₂ Methanol Synthesis Contact Process Ostwald Process PCl₅ dissociation HI decomposition

Kp (Pressure Equilibrium Constant)

Partial Pressures (atm)
Formula: Kp = Kc(RT)Δn
Where R = 0.0821 L·atm/(mol·K), T = temperature (K), Δn = change in moles of gas

Ka/Kb (Acid-Base Equilibrium)

Acetic acid (Ka=1.8×10⁻⁵) HF (Ka=6.8×10⁻⁴) Ammonia (Kb=1.8×10⁻⁵) Pyridine (Kb=1.7×10⁻⁹)
Key Relationships:
• Ka = [H⁺][A⁻] / [HA]
• Kb = [OH⁻][BH⁺] / [B]
• Ka × Kb = Kw = 1.0 × 10⁻¹⁴ (at 25°C)
• pKa = -log(Ka), pKb = -log(Kb)
• pKa + pKb = 14 (at 25°C)

ICE Table Solver

ICE = Initial, Change, Equilibrium

H₂ + I₂ ⇌ 2HI N₂O₄ ⇌ 2NO₂ PCl₅ dissociation Water-gas shift Acetic acid dissociation Ammonia in water
ICE Table
Reactant A Reactant B Product C
Initial (M)
Change (M)
Equilibrium (M)
Instructions:
1. Enter initial concentrations
2. Click Solve to find equilibrium concentrations
3. The solver will determine 'x' from the equilibrium expression
Understanding Equilibrium Constants
What is Chemical Equilibrium?

Chemical equilibrium occurs when the forward and reverse reaction rates are equal, resulting in constant concentrations of reactants and products.

Types of Equilibrium Constants
Kc (Concentration Equilibrium Constant)
For: aA + bB ⇌ cC + dD
Kc = [C]^c [D]^d / [A]^a [B]^b
Kp (Pressure Equilibrium Constant)
Kp = (P_C)^c (P_D)^d / (P_A)^a (P_B)^b
Relationship: Kp = Kc(RT)^Δn
Ka (Acid Dissociation Constant)
For: HA ⇌ H⁺ + A⁻
Ka = [H⁺][A⁻] / [HA]
Kb (Base Dissociation Constant)
For: B + H₂O ⇌ BH⁺ + OH⁻
Kb = [BH⁺][OH⁻] / [B]
Interpreting K Values
  • K >> 1: Products favored at equilibrium (reaction goes nearly to completion)
  • K ≈ 1: Significant amounts of both reactants and products
  • K << 1: Reactants favored at equilibrium (little product formed)
Reaction Quotient (Q)

Q has the same form as K but uses current concentrations (not equilibrium values):

  • Q < K: Reaction proceeds forward (toward products)
  • Q = K: System at equilibrium
  • Q > K: Reaction proceeds backward (toward reactants)
ICE Table Method

Initial, Change, Equilibrium - A systematic way to track concentrations:

  1. Write initial concentrations
  2. Define change in terms of x (stoichiometry matters!)
  3. Write equilibrium concentrations as (Initial ± Change)
  4. Substitute into K expression and solve for x
  5. Calculate final equilibrium concentrations
Le Chatelier's Principle

When a system at equilibrium is disturbed, it shifts to counteract the disturbance:

  • Add reactant: Shifts toward products
  • Add product: Shifts toward reactants
  • Increase temperature: Shifts in endothermic direction
  • Increase pressure: Shifts toward fewer moles of gas
Common Equilibrium Constant Values
Compound Type Value (25°C)
Acetic acid (CH₃COOH)Ka1.8 × 10⁻⁵
Hydrofluoric acid (HF)Ka6.8 × 10⁻⁴
Ammonia (NH₃)Kb1.8 × 10⁻⁵
Water (H₂O)Kw1.0 × 10⁻¹⁴