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:
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:
- Ag+ (aq) + Fe2+ (aq) ⇌ Ag (s) + Fe3+ (aq)
- N2 (g) + 3H2 (g) ⇌ 2NH3 (g)
- 2SO2 (g) + O2 (g) ⇌ 2SO3 (g)
Answer 1:
-
- Kc =
- [Ag (s)] is not included in the equilibrium expression as it is a solid
Answer 2:
-
- Kc =
Answer 3:
-
- Kc =
- Kc =