Question

Which of the following has the least surface tension.
A. Benzene
B. Acetic acid
C. Diethyl ether
D. Chlorobenzene

Answer 1

Hint: We should firstly learn the concept of surface tension and then discuss what causes surface tension. Talking about vapour pressure it is basically the pressure, surface tension is responsible for the shape of a liquid drop.

Complete answer:
Firstly we will talk about the surface tension. It is the tension basically caused by the liquid film which is caused by the attraction of the particles in the surface layer by the bulk of liquid and further tends to minimise the surface area. We should know that the surface tension is responsible for the shape of a liquid drop. Now we will discuss how this happens firstly when the there is a force of attraction between the particles. On the other hand, there must be the adhesive force which can be determined through the presence of vapour pressure then we must know that more is the vapour pressure least is the surface tension and vice versa. Then talking about vapour pressure it is basically the pressure which is exerted by the vapour in the thermodynamic equilibrium. This also works in a closed system. So more is the vapour pressure least is surface tension.
Diethyl ether has the least surface tension as it has the highest vapour pressure amongst the other three.
Hence option (C) is correct as “Diethyl ether” has the least surface tension.

Note: The concept of surface tension basically depends upon the surface area of the material. The surface area of the sphere is minimum, that’s why surface tension is maximum. Due to surface tension only formation of droplets takes place due to formation of cohesive forces.