Answer: A chemical equilibrium exists when the rate at which reactants form products is the same as the rate at which products form reactants.
Explanation:
When the concentration of both the reactants and products do not change with time then it means the chemical reaction has reached to a state of chemical equilibrium.
For example, [tex]CO(g) + Cl_{2}(g) \rightleftharpoons COCl_{2}(g)[/tex]
Therefore, we can conclude that a chemical equilibrium exists when the rate at which reactants form products is the same as the rate at which products form reactants.