Dynamic Equilibrium

Dynamic Equilibrium

1. Occurs in reversible reactions, when the forward and backward rate are equal

   • It needs a closed system (no reactants or products can escape)

2. Pressure (gas) / concentration (solution)

   • 2NO2 (g) = N2O4 (g) Brown : Colourless 2 moles: 1 mole
     • If pressure is increased, the equilibrium moves to where there are fewer molecules.
       • More N2O4 is produced therefore the container looks more colourless

3. Temperature

   • 2NO2 (g) = N2O4 (g) Brown : Colourless
     • Forward reaction is exothermic (ΔH= -ve) therefore the backward reaction is endothermic ( ΔH= +ve)
     • If temperature is increased, the equilibrium moves to the endothermic direction
       • More NO2 (higher yield of NO2) formed therefore the container looks more brown

4. Catalysts have no overall effect on equilibrium as they speed up the forward + reverse reaction equally

5. 3H + N2 = 2NH3 ΔH= -ve

   • Temp increased - the equilibrium will move to 3H + N2 because it is the endothermic direction
   • Pressure increased - the equilibrium will move to 2HN3 because there are fewer molecules