Question

How are vapour pressure and boiling point related?

Answer 1

Hint: As we know that boiling point is the temperature at which vapour pressure of a liquid becomes equal to the atmospheric pressure. And 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.

Complete answer::
- It is found that vapour pressure and boiling point are inversely proportional to each other. We can say that the boiling point increases as the vapour pressure decreases or vice versa.
- It is found that if the intermolecular forces are strong then the molecules will be strongly attracted to each other, and the vapour pressure will be low and a large amount of energy will be added to separate the molecules. Hence, the boiling point will be high.
- Whereas, if the intermolecular forces are weak, then liquid will have high vapour pressure, little amount of energy will be added to separate the molecules. And hence the boiling point will be low.
- Hence, we can say that vapour pressure and boiling point are inversely proportional to each other.

Note:
- As we know that if there are less intermolecular forces in the liquid, then it has a high vapour pressure, and a small amount of heat supply will be required to split molecules, hence the boiling point will be low.
- Whereas, if there are strong intermolecular forces in the liquid, then molecules will be strongly attracted to each other. Less molecules will break to convert into vapours. So, vapour pressure will be low. Hence, the boiling point will be high.