Reaction Quotient Calculator Formula

Understand the math behind the reaction quotient calculator. Each variable explained with a worked example.

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Formulas Used

Reaction Quotient (Q)

q = (pow(conc_c, coeff_c) * pow(conc_d, coeff_d)) / (pow(conc_a, coeff_a) * pow(conc_b, coeff_b))

Variables

VariableDescriptionDefault
conc_cConcentration of Product C(M)0.1
coeff_cCoefficient of C1
conc_dConcentration of Product D(M)0.1
coeff_dCoefficient of D1
conc_aConcentration of Reactant A(M)0.5
coeff_aCoefficient of A1
conc_bConcentration of Reactant B(M)0.5
coeff_bCoefficient of B1

How It Works

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

    • Worked Example

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

    conc_c = 0.1coeff_c = 1conc_d = 0.1coeff_d = 1conc_a = 0.5coeff_a = 1conc_b = 0.5coeff_b = 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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