Q.Explain micelle formation in soap solution.

Step 1. Structure of a soap molecule. A soap molecule has a long hydrophobic hydrocarbon chain (the tail) attached to a hydrophilic ionic group, typically a carboxylate (the head).

Step 2. Behaviour at low concentration. At low concentration in water, soap behaves as a normal (fully dissolved) electrolyte, with individual soap ions dispersed in solution.

Step 3. Behaviour above the critical concentration. Once the soap's concentration rises above a certain threshold, the individual soap molecules/ions associate together and form colloidal-sized aggregates called micelles, rather than staying as separate dissolved ions.

Step 4. Arrangement within a micelle. Within each spherical micelle, the hydrophobic hydrocarbon tails of many soap molecules point inward, clustering together at the centre of the sphere away from the surrounding water (since they have no affinity for water), while the hydrophilic (carboxylate) heads lie on the outer surface of the sphere, in direct contact with the surrounding water molecules. …

Explaining associated-colloid (micelle) formation as given in Sections 11.9.2(c) and …

• Reversing the orientation -- the hydrophobic tails point INWARD (away from water) and the hydrophilic heads point OUTWARD (toward water), not the other way round. …