Question

CMC (Critical Micelle Concentration) is:
A) The concentration at which micelles are destroyed
B) The concentration at which micelles formation starts
C) The concentration of electrolyte added to destroy the micelles
D) The concentration of micelles at room temperature

Answer 1

Hint: To answer this question we should know that micelle is an aggregate of surfactant molecules dispersed in a liquid colloid. Now try to find the correct answer using this hint.

Complete answer :
Micelle - Micelle, in aqueous solution, forms an aggregate with the hydrophilic head regions in contact with the surrounding solvent, sequestering the hydrophobic single-tail regions in the micelle center.
Critical micelle concentration (CMC) - The concentration of surfactants above which micelles form and all additional surfactants added to the system will form micelles, is known as critical micelle concentration.
It is an important characteristic of a surfactant. Before the critical micelle concentration, the surface tension changes strongly with the concentration of the surfactant.
The CMC value for a given dispersant in a given medium depends on pressure, temperature, and concentration of other surface-active substances and electrolytes.
Here, we can conclude that Micelles only form above critical micelle temperature.

Therefore, we can conclude that the correct answer to this question is option B.

Note: We should also know that when surfactants are present above the critical micelle concentration (CMC), they can act as emulsifiers that will allow a compound that is normally insoluble in the solvent being used to dissolve.
Detergents clean by lowering the surface tension of water, making it easier to remove material from a surface.