In a closed system , equilibrium is said to be dynamic. Why?

In a closed system, equilibrium is said to be dynamic because even though there are no net changes in macroscopic properties, such as concentration or pressure, at the macroscopic level, at the microscopic level, there is continuous activity. In other words, reactions are still occurring, but the rates of the forward and reverse reactions are equal, resulting in a stable state.

The dynamic nature of equilibrium can be understood through the concept of microscopic reversibility. At equilibrium, the rate of the forward reaction is equal to the rate of the reverse reaction, meaning that reactants are converting to products at the same rate as products are converting back to reactants.

So, while there is no net change in the concentrations of reactants and products, individual molecules or particles are constantly in motion, undergoing reactions, and exchanging energy. The system is dynamic on the microscopic level even though it appears static on the macroscopic level.