alleryStart learning →The vapour pressure of water is the pressure exerted by water vapour under which condition?
AIn equilibrium with liquid water
BWhen all the liquid has boiled off
CWhen the container is fully open
DAt the moment the water freezes
Answer & Solution
Correct answer: A. In equilibrium with liquid water
1. Liquid water always has some vapour above it, because molecules keep leaving the surface.
2. In a closed container the vapour builds up until molecules return as fast as they leave.
3. The pressure of the vapour at that balance point is the vapour pressure of water.
4. It depends on temperature alone, rising steadily as the water gets hotter.
_Source: OpenStax Chemistry (CC BY 4.0), Ch 9 "Gases", section 9.3 Stoichiometry of Gaseous Substances, Mixtures, and Reactions_
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