Why do the concentrations of the reactants and products stay constant once a reaction has reached dynamic equilibrium?
Each substance is being made at the same rate as it is being used up.
Both the forward reaction and the reverse reaction have stopped.
The concentrations of reactants and products have become equal.
The forward reaction has stopped and only the reverse reaction continues.
124 exam-style questions on OCR GCSE Chemistry 5.3 Equilibria, covering 5.3.1 Reversible reactions and dynamic equilibrium and 5.3.2 Changing the position of equilibrium. Each one has a worked solution and a mark scheme showing where the marks go.