What do you mean by state of dynamic equilibrium?
During the evaporation of a liquid in a closed vessel, a stage is reached when the rate of evaporation becomes equal to the rate of condensation. In such a state, the system is not at rest though there is no change in the system because the amount of liquid level in the vessel does not change. This does not mean that evaporation has stopped. In fact, the number of molecules which escape from the liquid to the vapour phase (due to evaporation) becomes equal to the number of molecules which return to the liquid from the vapour phase (due to condensation). This state is known as dynamic equilibrium. At dynamic equilibrium state, the two opposing processes (evaporation and condensation) occur at an equal rate.
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