Question

The action of cleaning of oily dirt by soap is based on
A.Solubility in water
B.Hydrophilic property
C.Hydrophobic property
D.Presence of both hydrophilic and hydrophobic groups

Answer 1

Before solving this question, we should know what are soaps, their cleaning action, and then we can find the property on which this action depends on. A water-soluble compound that is salt of a fatty acid that is produced with the help of a saponification process is Soap. It is NaOH or KOH and vegetable oils or animal oils.

Complete answer:
The dirt is mostly oily and is insoluble in water. The soap contains sodium or potassium salts of long carboxylic acids. The carbon chains get dissolved in oil and the ionic end gets dissolved in water in case of the soaps, Thus molecules of soap form a structure that is called micelles. In this, the oil droplet has one side and the other side faces outside which is ionic. This is the reason they produce emulsion in water and when we wash the clothes, it dissolves the dirt.
Soap has two ends :
Hydrophilic end – It is the end that is dissolvable in water.
Hydrophobic end – It is the end that repels the water and is insoluble in it.
When soap comes in contact with water, the soap is arranged in a way that the hydrocarbon part is outside. When the molecules are aggregated it forms clumps then the hydrophobic tail comes inside of the cluster and the ionic end comes on the surface of the cluster. After this, soap can clean the oily dirt that is in the middle.

So, Option (D) Presence of both hydrophilic and hydrophobic groups is correct.

Note:
There are some features of soap – The harder soap will last longer as it will be dense. Soap helps in the basic cleaning. It has a long chain of carbons in which one side of the chain draws oil and the other side draws water. The soap which produces lather.