AQA A Level Chemistry

Revision Notes

1.8.3 The Equilibrium Constant, Kc

The Equilibrium Constant, Kc

Equilibrium expression & constant

  • The equilibrium expression links the equilibrium constant, Kc, to the concentrations of reactants and products at equilibrium taking the stoichiometry of the equation into account
  • So, for a given reaction:

aA + bB ⇌ cC + dD

the Kc is defined as follows:

Equilibria Equilibrium Expression, downloadable AS & A Level Chemistry revision notes

Equilibrium expression linking the equilibrium concentration of reactants and products at equilibrium

  • Solids are ignored in equilibrium expressions
  • The Kc of a reaction is specific and only changes if the temperature of the reaction changes

Worked Example

Deducing equilibrium expressions

Deduce the equilibrium expression for the following reactions:

  1. Ag+ (aq) + Fe2+ (aq) ⇌ Ag (s) + Fe3+ (aq)
  2. N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
  3. 2SO2 (g) + O2 (g) ⇌ 2SO3 (g)

Equilibrium Constant Concentrations Worked Example equations, downloadable AS & A Level Chemistry revision notes

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