The vapour pressure of a liquid is the pressure exerted by its vapour when
Correct answer: B. the vapour is in dynamic equilibrium with the liquid in a closed container
- A. the liquid has completely evaporated
- B. the vapour is in dynamic equilibrium with the liquid in a closed container
- C. the liquid is boiling in an open vessel
- D. the container is completely empty of air
Explanation
In a closed vessel evaporation and condensation eventually occur at the same rate, and the constant pressure of vapour at that point is the equilibrium vapour pressure of the liquid at that temperature. It depends only on the liquid and the temperature, never on the volume of the container or the amount of liquid present. In an open vessel equilibrium is never reached because vapour escapes.
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About Evaporation, Boiling Point and Vapour Pressure
Evaporation is the escape of higher-energy molecules from a liquid surface, while vapour pressure is the pressure exerted by vapour in equilibrium with that liquid. The topic distinguishes evaporation from boiling and relates both to temperature, intermolecular forces, surface area, atmospheric pressure and the boiling point.
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