Free Reaction Quotient Calculator

Calculate the reaction quotient (Q) for a reaction aA + bB → cC + dD from current concentrations, and compare it to K to predict reaction direction.

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Reaction Quotient (Q)

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Reaction Quotient (Q) vs Concentration of Product C

Reaction Quotient

Formula

Q = [C]^c × [D]^d / ([A]^a × [B]^b)

Where:

  • Q = reaction quotient
  • [X] = current concentration of species X
  • a, b, c, d = stoichiometric coefficients
  • Compare Q to K:

  • Q < K → reaction proceeds forward (toward products)
  • Q > K → reaction proceeds backward (toward reactants)
  • Q = K → system is at equilibrium
  • Example Calculation

    A + B → C + D. Current: [A]=0.5, [B]=0.5, [C]=0.1, [D]=0.1. All coefficients = 1.

    1. 01Q = [C]^c[D]^d / [A]^a[B]^b
    2. 02Q = (0.1)¹(0.1)¹ / (0.5)¹(0.5)¹
    3. 03Q = 0.01 / 0.25
    4. 04Q = 0.04

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