Question

How do you find vapour pressure of water at a given temperature?

Answer 1

Hint: The vapour pressure is the pressure exerted when the molecules leave their spaces and leave from one surface at the same rate as they return. It is known that vapour pressure is low if the intermolecular force between molecules is strong.

Complete answer:
- Vapour pressure is a measure of the tendency of a material to change into the gaseous or vapour state. It is known to increase with increase in temperature.
- Raoult’s law states that the vapour pressure of a solvent above a solution is equal to the vapour pressure of the pure solvent at the same temperature scales by the mole fraction of the solvent present.
- The vapour pressure is affected by various factors including temperature, and the nature of the substance.
- The vapour pressure of water is the pressure at which water vapour is in equilibrium with its condensed state.
- In other words, if the temperature is kept constant and the pressure is increased, water is supposably condensed.
- In order to calculate the vapour pressure of water, the Antoine equation is most commonly used. This equation is derived from the Clausius-Clapeyron relation.

Note: As we know that, if there are strong intermolecular forces in the liquid, then the molecules will be strongly attracted to each other. Less molecules will break to convert into vapours. So, vapour pressure will be low.