Aliquid is placed in an evacuated, sealed flask. when will this closed system reach dynamic equilibrium? when all of the liquid has evaporated to form a vapor when liquid and vapor are present but evaporation stops when the rate of evaporation equals the rate of condensation when the volume of liquid equals the volume of vapor

If we ignore temperature equilibrium (since no data given), then dynamic equilibrium when the rate of evaporation equals the rate of condensation over a finite period of time and under constant temperature.

This is because at *dynamic* equilibrium, evaporation and condensation are both taking place continuously.  If the rates are equal, then the mass of vapour and mass of liquid phases do not change, hence equilibrium.  Dynamic because changes are still taking place.

The molecules contain like 54 of water