Question

Surface tension of lyophilic sols is:
A: Lower than that of ${H_2}O$
B: Equal to that of ${H_2}O$
C: More than that of ${H_2}O$
D: None of these

Answer 1

Hint: Surface tension is defined as the property of the surface of liquid that allows it to resist an external force. It is tension of surface film of a liquid caused by attraction of the particles in the surface layer by bulk of the liquid. It is calculated as force per unit length along which the force acts.

Complete step by step answer:
-Colloids are the homogeneous and non crystalline substances made up of ultramicroscopic particles on which one substance is dispersed through the other substance. The substance which is dispersed is called dispersed phase and the substance in which it is dispersed is called dispersed medium.
-Lyophilic sols are produced by direct mixing of substances.
-Lyophilic sols are highly stable.
-These sols have strong forces of attraction between dispersed phase and dispersion medium. Dispersed medium can be separated from sols by physical methods like evaporation due to which these are also called reversible sols.
-Examples of such sols include rubber, starch etc. lyophilic sols water loving. These sols have a large affinity for water which decreases their surface tension. This means surface tension of lyophilic sols is less than surface tension of water.

So the correct answer is option A that is Lower than that of ${H_2}O$.


Note:Like lyophilic there are lyophobic sols as well. lyophobic sols are not stable like lyophilic sols. Their method of formation is also different as compared to lyophilic sols. These are not formed by simple mixing of its constituents. These are irreversible in nature. This means dispersed medium can’t be separated from these sols.