Question

At CMC, the surfactant molecules:
A. Decompose
B. Become completely soluble
C. Associate
D. dissociate

Answer 1

Hint: CMC is critical micelle concentration is a surfactant which reacts. Surfactants are used or its basic use includes removing dirt, or greasing etc from the clothes. Let us find out in what way it reacts to answer this question.

Complete step by step answer:
CMC is a critical micelle concentration associated with surfactant molecules and forms micelles. There is a condition that at a particular temperature only it will associate and that temperature is known as kraft temperature. Hence at CMC or critical micelle concentration and krafts temperature the surfactant molecules associate and form micelles. These micelles help in removing dirt, grease, dirt, etc from clothes.

So, the correct answer is Option C.

Note: We can measure critical micelle concentration with the help of a tensiometer by measuring the surface tension. When it comes to surfactant, the surface tension is linearly dependent on the log of the concentration over a very large range. Above critical micelle concentration, the surface tension is independent of concentration. CMC results from the intersection between the regression straight line of a linearly dependent region and a straight line passing through the plateau.
As the concentration of the surfactant is increased, the process of adsorption takes place at the surface until it is fully over laid, which leads to the minimum value of SFT (surface tension). Volume phase micelles are formed above the transition concentration described as critical micelle concentration.