Dynamic Equilibrium (AQA GCSE Combined Science: Synergy: Physical Sciences): Revision Note
Exam code: 8465
Written by: Stewart Hird
Updated on
Dynamic equilibrium
When a reversible reaction takes place in a closed system (where reactants and products cannot escape), the reaction reaches dynamic equilibrium
At dynamic equilibrium, the rates of the forward and reverse reactions are equal
The concentrations of reactants and products remain constant (though not necessarily equal)
The relative amounts of all the reactants and products at equilibrium depend on the conditions of the reaction
If a change is made to the conditions of a system at equilibrium, the system automatically moves to oppose the change
Examiner Tips and Tricks
Dynamic equilibrium does not mean the reaction has stopped. Both the forward and reverse reactions are still occurring, just at the same rate. A common wrong answer is "the reactions stop" or "no more product is being made."
Another key error is describing the wrong conditions for equilibrium. The system must be in a closed system (no substances can escape), not just "at a fixed temperature" or "at constant pressure."
Finally, don't confuse constant with equal. At dynamic equilibrium, the concentrations of reactants and products are constant (they don't change over time), but they are not necessarily equal to each other.
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