Question

The surface tension of Lyophilic sols is:

• A. Lower than that of ${\mathrm{H}}_2\mathrm{O}$
• B. More than that of ${\mathrm{H}}_2\mathrm{O}$
• C. Equal to that of ${\mathrm{H}}_2\mathrm{O}$
• D. Either less or more concerning${\mathrm{H}}_2\mathrm{O}$ depending on the nature of the disperse phase.

Answer 1

The correct option is A

Lower than that of ${\mathrm{H}}_2\mathrm{O}$

Explanation for the correct option:

[A] Lower than that of ${\mathrm{H}}_2\mathrm{O}$

• Lyophilic sols are the colloids where the particles of the Dispersed phase have a stronger affinity or binding with the particles of the Dispersion Medium in which the particles of the Dispersed phase are suspended.
• Its higher affinity towards water makes it hydrated and results in higher viscosity.
• Any solution with a higher viscosity, leads to a decrease in surface tension than the Dispersion medium.
• So, the Surface tension of Lyophilic sols is lower than that of${\mathrm{H}}_2\mathrm{O}$.

So, option[A] is correct.

Explanation for the incorrect option:

[B] Higher than that of ${\mathrm{H}}_2\mathrm{O}$

• Higher affinity of Lyophilic sols towards water makes it hydrated and results in higher viscosity.
• Any solution with a higher viscosity, leads to a decrease in surface tension than the Dispersion medium.
• So, the Surface tension of Lyophilic sols is lower than that of ${\mathrm{H}}_2\mathrm{O}$ and more in the case of Lyophobic sols.

So, option[B] is incorrect.

[C] Equal to that of ${\mathrm{H}}_2\mathrm{O}$

• Higher affinity of Lyophilic sols towards water makes it hydrated and results in higher viscosity.
• Any solution with a higher viscosity, leads to a decrease in surface tension than the Dispersion medium.
• So, the Surface tension of Lyophilic sols is lower than that of${\mathrm{H}}_2\mathrm{O}$ and not equal to that of${\mathrm{H}}_2\mathrm{O}$.

So, option[C] is incorrect.

[D] Either less or more concerning${\mathrm{H}}_2\mathrm{O}$ depending on the nature of the disperse phase.

• Whatever the nature of the particle may be, If it's a Lyophilic sol, then it would have a higher affinity towards the water.
• And so, it would lead to higher viscosity and thus, lower surface tension.
• So, it is not dependent on the nature of the particle when we know it's a Lyophilic sol.

So, option[D] is incorrect.

Hence, the surface tension of Lyophilic sols is [A] Lower than that of${\mathrm{H}}_2\mathrm{O}$.