Answer. Equilibrium state is attained in reversible reactions. At equilibrium state reaction does riot stop, because not only reactants react to form the products but side by side products also react to form the reactants. For example, in case of reaction between hydrogen and iodine vapours; at equilibrium state; as much amount of hydrogen and iodine react to form hydrogen iodide, the corresponding amount of hydrogen iodide decomposes to form hydrogen and iodine. As a result concentrations of reactants and products remain the same and reaction does not stop.