Reversibility and dynamic equilibria
2 marks · HardExplain, in terms of particle behaviour, why the concentrations of reactants and products remain constant in a sealed container when a reversible reaction has reached dynamic equilibrium.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
Must show: rate of forward and backward reactions are equal, particles continue to react in both directions
Also accept: the rate at which reactants form products equals the rate at which products reform reactants; the forward and reverse reactions happen at the same rate, so overall concentrations do not change
Common mistakes: saying reactions have stopped; ignoring ongoing particle collisions
Show mark scheme and worked solution
Marking points
M1 · 1 mark · States or explains that the rate of the forward reaction equals the rate of the backward reaction.
A1 · 1 mark · States or explains that particles continue to react in both directions but concentrations remain constant.
Worked solution
At dynamic equilibrium, the rate of the forward reaction equals the rate of the backward reaction. This means that, although particles of reactants are continuously forming products and vice versa, both reactions occur at the same rate so the overall concentrations of reactants and products remain constant.