Practice question · Multiple choice
Vapour pressure depends purely on temperature, yet doubling the surface area of a liquid doubles the rate of evaporation. Why does an open dish of water evaporate faster without exhibiting a higher vapour pressure?
Hints
- What condition is strictly required for a dynamic phase equilibrium to establish?
- How does an intensive thermodynamic property differ from an extensive kinetic rate?
Show the answer
D. The rate of condensation matches evaporation only in a closed system
Why
Equilibrium vapour pressure reflects a dynamic balance where forward and reverse rates balance in a closed vessel. In open air, evaporation rate scales with area, but equilibrium is never attained; vapour pressure itself remains an intensive thermodynamic property governed by temperature.
Practise Physical Equilibria and Phase Diagrams
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