Answer:
When a system is at equilibrium in terms of concentration what happens is that the rate of change of the concentration of the product and the reactants does not vary or change with time.
Step-by-step explanation:
What is equilibrium?
A chemical reaction is in equilibrium when the concentrations of reactants and products are constant - their ratio does not vary.
Equilibrium does not necessarily mean that reactants and products are present in equal amounts. It means that the reaction has reached a point where the concentrations of the reactant and product are unchanging with time, because the forward and backward reactions have the same rate.