Question

Soft soap are:
A. sodium salts of fatty acids
B. potassium salts of fatty acids, containing excess of free alkali
C. potassium salts of fatty acids, containing no free alkali
D. calcium salts of fatty acids

Answer 1

Hint: To answer this question we should know what is hard and soft soap. The soft and hard nature of soap depends upon the alkaline solution. The alkaline solution of soft alkali metal gives the soft soap and the alkaline solution of hard alkali metal gives the hard soap.

Complete answer:
Soap is manufactured by fat, oils and alkaline solutions. The sodium and potassium salt of long fatty acid chains are known as soaps. The process of making soap is known as saponification. During saponification reaction, oil and fat containing fatty acid react with a base such as sodium/potassium hydroxide or chloride to make soap and alcohol.

Potassium is a relatively softer metal than sodium. The sodium salt of long fatty acid chains is known as hard soap whereas the potassium salt of long fatty acid chains is known as soft soap. Soft soap is made up of oil and fat. The soft soap does not contain free alkali that is why the soft soap is smooth. So, Soft soap are potassium salts of fatty acids, containing no free alkali.

Therefore, option (C) potassium salts of fatty acids, containing no free alkali, is the correct answer.

Note: As hard and soft both soap is made by an alkaline salt solution so the mixture of saponification reactions is basic. The solution of hard soap has free alkali ions so the hard soaps are slippery and rough. Soft soap does not contain free alkali hence smooth. Soft soap is used in shampoo, body showers and shaving creams, etc. the hard soap is used for toilet purposes.