Question

Micelles are:
A) Emulsion-cum gel
B) Adsorbed catalyst
C) Associated colloids
D) Ideal solutions

Answer 1

Micelles are formed when soaps are dissolved in water. Soaps are sodium or potassium salts of long chain carboxylic acids. Soaps are represented as ${\text{RCOONa}}$. At high concentration, soap forms an ionic micelle.

Complete step by step answer:
We know that when soaps are dissolved in water at low concentration, soaps dissociate into carboxylate ion $\left( {{\text{RCO}}{{\text{O}}^ - }} \right)$ and sodium ion $\left( {{\text{N}}{{\text{a}}^ + }} \right)$. The dissociation reaction of soap is as follows:
${\text{RCOONa}} \to {\text{RCO}}{{\text{O}}^ - } + {\text{N}}{{\text{a}}^ + }$
Thus, at low concentration, soap behaves as an electrolyte.
The carboxylate ion $\left( {{\text{RCO}}{{\text{O}}^ - }} \right)$ has two parts. One is the polar hydrophilic group $\left( {{\text{CO}}{{\text{O}}^ - }} \right)$ which is a water loving group and the non-polar hydrophobic group $\left( {\text{R}} \right)$ which is water hating.
The polar hydrophilic group $\left( {{\text{CO}}{{\text{O}}^ - }} \right)$ is called the head while the non-polar hydrophobic group $\left( {\text{R}} \right)$ is called the tail.
When the concentration of soap is increased, the soap molecules arrange themselves in a typical manner which is known as micelle.
Micelles are spherical structures in which the hydrophilic end is on the outer side of the sphere and the hydrophobic end is on the inner side of the sphere. The hydrocarbon chains of soap are hydrophobic and the ionic ends are hydrophilic.
Thus, at high concentration, soap molecules aggregate to form micellar particles.
We know that the substances which act as electrolytes at lower concentration and aggregate to form particles at higher concentration are known as associated colloids.
Thus, micelles are associated colloids.

Thus, the correct option is (C) false.

Note: Do not confuse between hydrophobic and hydrophilic end of soap. Remember that the hydrocarbon group of soap is responsible for the formation of micelle. Hydrophilic means water loving and hydrophobic means water hating.