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Explain the cleansing action of detergents



  • Detergents are sodium salts of long chain benzene sulphonic acids (eg. CH 3 -(CH 2 ) 11 - C 6 H 4 -SO 3 - Na + ) or sodium salts of long chain alkyl hydrogensulphates (eg . CH 3 -(CH 2 ) 10 -CH 2 -SO 4 - Na + ). 

They have a similar but stronger cleansing action as compared to that of soap.

Cleansing Action :

When detergent is dissolved in water, two types of arrangements of these molecules are seen:

1. On the surface of water: 

The detergent molecules present on the surface of water align themselves in such a way that the hydrophilic end is inside water and the hydrophobic end faces outward

2. Inside water: 

The detergent molecules which are completely inside water form a cluster . The arrangement is such that the hydrophobic tails are towards the inside of the cluster and hence their contact with water is avoided whereas the hydrophilic ends are present on the surface . This type of arrangement is known as micelle .


  • When a dirty cloth is put in a detergent solution (detergent+water), the hydrophobic part dissolves the oil and dirt from the surface of cloth
  • This is how dirt and oil is entrapped inside the micelle with the help of the hydrophobic part. 
  • When the cloth is agitated , these micelles are removed from the surface of cloth and they disperse in water, thereby removing the oil and dirt. 
  • The cloth gets cleaned after thoroughly rinsing it with water 3-4 times.


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CA Maninder Singh is a Chartered Accountant for the past 12 years and a teacher from the past 16 years. He teaches Science, Economics, Accounting and English at Teachoo