Question

State true or false: A liquid having high vapour pressure has low boiling point.
[A] True
[B] False

Answer 1

Hint: Vapour pressure is the pressure exerted by the gas on liquid (or solid) in a closed system at a particular temperature. If we increase the vapour pressure by heating, the pressure exerted by the atmosphere on the liquid decreases thus evaporates fast.

Complete step by step answer:
To answer this question, firstly let us understand what is the vapour pressure and boiling point of a liquid.
We know that boiling is the process of a liquid turning into vapour when subjected to heat. A substance boils when the heat reaches the boiling temperature of the substance. This is a phase change and it is a physical process, not a chemical reaction.
This change occurs when the vapour pressure of the liquid is equal to the atmospheric pressure exerted by the liquid.
Every liquid (or any substance) has a specific boiling point, i.e. a specific temperature at which its phase changes from liquid to vapour.
On the other hand we have vapour pressure which is the upward pressure that the molecules of the liquid face when they are trying to leave the surface of the liquid through evaporation. In simple words, we can say that it is the pressure which is exhibited by the vapour present above the liquid surface.
Like boiling point, every substance has a specific vapour pressure too.
When the vapour pressure of a liquid reaches the atmospheric pressure, it starts to boil.
As a result of vapour pressure the amount of atmospheric pressure exerted on the liquid decreases. Therefore, liquids with high vapour pressure will have a lower boiling point.
The statement given to us is- A liquid having high vapour pressure has low boiling point.
We can understand from the above discussion that the statement is correct.
So, the correct answer is “Option A”.

Note: Difference in boiling points of different substances is the result of different vapour pressure of these substances. This difference is present due to different intermolecular forces acting between their molecules. We can increase the vapour pressure by heating the liquid. As a result, it will overcome the atmospheric pressure and form vapour bubbles inside the bulk of the substance.