Question

Cleansing action of soap is due to

• A. adsorption of oil and grease on the hydrophobic centres of soap micelles and, which are then be washed away
• B. adsorption of oil and grease on the hydrophilic centres of soap micelles and, which are then be washed away
• C. adsorption of oil and grease on the hydrophilic and hydrophobic centres of soap micelles and, which are then be washed away
• D. it is not at all related with micelles

Answer 1

The correct option is A adsorption of oil and grease on the hydrophobic centres of soap micelles and, which are then be washed away

Soap is an excellent cleanser because of its ability to act as an emulsifying agent. An emulsifier is capable of dispersing one liquid into another immiscible liquid. This means that while oil (which attracts dirt) does not naturally mix with water, soap can suspend oil/dirt in such a way that it can be removed.

Grease and oil are non-polar and insoluble in water. When soap and soiling oils are mixed, the nonpolar hydrocarbon portion of the micelles break up the non-polar oil molecules. A different type of micelle then forms, with nonpolar soiling molecules in the center. Thus, grease and oil and the dirt attached to them are caught inside the micelle and can be rinsed away.