GCSE Chemistry revision

The effect of changing concentration

Reversible reactions and dynamic equilibrium

AQA 4.6.2.5 Higher Tier only

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Increasing the concentration of a reactant causes the equilibrium to shift to the opposite side (towards the products) to counteract the change.
For example, adding more nitrogen to the Haber process increases nitrogen concentration, shifting the equilibrium to the right and producing more ammonia.

1. Effect of Concentration on Equilibrium AQA

Increasing the concentration of a reactant causes the equilibrium to shift to the opposite side (towards the products) to counteract the change.
For example, adding more nitrogen to the Haber process increases nitrogen concentration, shifting the equilibrium to the right and producing more ammonia.

Once dynamic equilibrium is established, the concentrations of all reactants and products remain constant over time, even though both forward and reverse reactions continue occurring at equal rates.
Example: In the sealed system N₂O₄(g) ⇌ 2NO₂(g), the brown colour of NO₂ gas remains constant because the relative amounts of N₂O₄ and NO₂ stop changing once equilibrium is reached.

2. Constant Concentrations AQA

Once dynamic equilibrium is established, the concentrations of all reactants and products remain constant over time, even though both forward and reverse reactions continue occurring at equal rates.
Example: In the sealed system N₂O₄(g) ⇌ 2NO₂(g), the brown colour of NO₂ gas remains constant because the relative amounts of N₂O₄ and NO₂ stop changing once equilibrium is reached.