Question

Sodium or potassium salts of higher fatty acids are called [MP PET $2003$]
A.Soaps
B.Terpenes
C.Sugars
D.Alkaloids

Answer 1

Hint: Fatty acids are the building blocks of fats in our body system, consisting of long chains of lipid-carboxylic acid found in oils and fats and also in cell membranes as the major component of glycolipids and phospholipids. Salts of fatty acids such as sodium or potassium salts of fatty acids can be used as surface active reagents.

Complete answer:Fats are triglycerides of higher-order fatty acids such as oleic acid, stearic acid, palmitic acid, etc. We can use the sodium or potassium salts of fatty acids as surface active agents or surfactants.

Surface active agents or surfactants are chemical substances that concentrate at the surface of the solution and form surface films hence they reduce the surface tension of the solution. Thereby it helps in removing dirt and dust.

Normal water does not remove dirt from skin and clothes as dirt is oily or greasy in nature. Hence sodium or potassium salts of higher fatty acids or soaps that are water-soluble are able to remove this dirt from water. When a dirty cloth is kept in a soap solution, the long non-polar hydrocarbon tail of soap molecules directs towards the oily dirt particles whereas polar heads are directed towards the water. Therefore forms spherical micelles which are attracted to water and carry dirt particles along with them. In this way, surfactants remove dirt from clothes.


Therefore sodium or potassium salts of higher fatty acids are called soaps.

Thus, option (A) is correct.

Note: Potassium soaps are more soluble as compared to sodium salts. That’s why sodium soaps are used to make bar soap while potassium soaps are used to make liquid soap, shaving cream, etc. Because potassium soaps are softer and more water soluble than sodium soaps.