GCSE Chemistry revision

The effect of pressure changes on equilibrium

Reversible reactions and dynamic equilibrium

AQA 4.6.2.7 Higher Tier only

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Pressure is a measure of the number of particles per unit volume, so the equilibrium shifts to the side with fewer molecules to reduce pressure when pressure is increased.
In the Haber process, increasing pressure shifts the equilibrium to the right (2 molecules of ammonia) rather than the left (4 molecules: 1 nitrogen + 3 hydrogen).
Decreasing the pressure shifts the equilibrium to the side with more molecules (the left in the Haber process) to increase pressure back up.

1. Effect of Pressure on Equilibrium AQA

Pressure is a measure of the number of particles per unit volume, so the equilibrium shifts to the side with fewer molecules to reduce pressure when pressure is increased.
In the Haber process, increasing pressure shifts the equilibrium to the right (2 molecules of ammonia) rather than the left (4 molecules: 1 nitrogen + 3 hydrogen).
Decreasing the pressure shifts the equilibrium to the side with more molecules (the left in the Haber process) to increase pressure back up.

A reversible reaction reaches dynamic equilibrium in a closed system (where no reactants or products can enter or escape) when the rate of the forward reaction equals the rate of the reverse reaction.
Example: In a sealed bottle of carbonated water, carbon dioxide gas dissolves into the liquid at the exact same speed that dissolved carbon dioxide escapes back into the gas space above it.

2. Equal Reaction Rates AQA

A reversible reaction reaches dynamic equilibrium in a closed system (where no reactants or products can enter or escape) when the rate of the forward reaction equals the rate of the reverse reaction.
Example: In a sealed bottle of carbonated water, carbon dioxide gas dissolves into the liquid at the exact same speed that dissolved carbon dioxide escapes back into the gas space above it.