Question

Assertion: Mixture is agitated in a washing machine. Agitation is necessary to get clean clothes.
Reason: To wash away the loosened dirt particle in the form of micelles from the surface of cloth, agitation is necessary.
$(a) {\text{ }}$Both assertion and reason are correct and reason is the correct explanation for assertion.
$(b) {\text{ }}$Both assertion and reason are correct but reason is not the correct explanation for assertion.
$(c) {\text{ }}$Assertion is correct but reason is not.
$(d) {\text{ }}$Both assertion and reason are incorrect.

Answer 1

- Hint: In micelles, the end towards the oil droplet is the hydrophobic end whereas the other end with the ionic faces towards outside is the hydrophilic end. It forms an emulsion in the water which helps in dissolving the dirt.

Complete step-by-step solution:
The micelle is an aggregate of surfactants dispersed in a colloidal solution. The micelle is so formed that the hydrophilic “head” regions are in contact with the surrounding aqueous solvent whereas the hydrophobic “tail” regions are in the micelle centre. The balance between the entropy and the enthalpy is responsible for the spontaneous formation of the micelles. In water, the driving force for the micelle formation is the hydrophobic effect. When the soap is added to the water, the micelle formation takes place. The hydrophilic end dissolves in water and is attracted to it whereas the hydrophobic end is dissolved in hydrocarbons and is water repulsive. When the soap is in the form of the micelles, it has the ability to wash away the oily dirt accumulated at the centre.
Agitation is the mechanism of putting something into motion by stirring or shaking. The washing machine has bottom washer fins for moving back and forth and a spiral top which helps in guiding the clothes to bottom washer fins. So, it moves the water and detergent along with the clothes and gets the dirt out.

So, the correct answer is the option $(a)$.

Note: The micelles so formed in this process remains as the colloidal solution. The soap solution appears to be cloudy, this is because of the formation of this colloidal solution only that the light is scattered.