Question

At high concentration of soap in water, soap behaves as ____________.
(i) molecular colloid
(ii) associated colloid
(iii) macromolecular colloid
(iv) lyophilic colloid


NCERT Class XII
Chemistry - Exemplar Problems

Chapter 5. Surface Chemistry

Answer 1

The answer is: (ii) Associated colloid.

Answer 2

At high concentration of soap in water, soap behaves as (ii) associated colloids.

Explanation:

Soap molecules are polar sodium salts of fatty acids. They have a long hydrocarbon chain with $\bold{-COO^- ions}$ as polar end. The lone hydrocarbon chain acts as hydrophobic part whereas the polar end is hydrophilic part. When we mix soap in water, these molecules associated to form micelle.

This association takes place in such a way that the hydrophilic part remains inside whereas hydrophobic part remains outside. Therefore, they form associated colloids.