What is the difference between the chemical composition of soaps and detergents. State in brief the action of soaps in removing an oily spot from a short. Why are soaps not considered suitable for washing where water is hard?

The Difference between the chemical composition of soaps and detergents are as follows:

1. Soaps are sodium (Na) salts or Potassium (K) salts of some long chain carboxylic acids whereas detergents are ammonium or sulphurated salts or long chains of carboxylic acids (COOH).

2. Soaps can’t form lather with hard-water but detergents can form lather with hard water as well as soft water.

3. Soaps are biodegradable and can be break into simpler substances but detergents are non-biodegradable and can be break into simpler substances.

4. Soaps are mild cleansing agents but detergents are strong cleansing agents and are much effective in removing oil and dirt.

Action of Soap in removing an oily spot from a shirt:

When a dirty cloth having oily spot is put in water containing dissolved soap, the oil is not dissolved in water. The soap molecules are salts of sodium and potassium of long chain carboxylic acid. The acid end of soap is hydrophilic i.e. water loving , and gets dissolved in water and the carbon chain dissolves in oil. Soap molecules forms micelles structure in which one end of the soap molecule is attached to the oil droplet and the other end towards the water. The formation of soap micelles thus removes oil particles from the surface and the surface is cleaned.

Soaps are not suitable for washing clothes when the water is hard because for washing the clothes, formation of lather is important to remove dirt from clothes. If the water is hard, it reacts with calcium and magnesium ions which are present in hard water and results in formation of calcium and magnesium salts which doesn’t gives lather. The precipitate formed gets sticks to clothes and interferes in the cleaning of clothes. Therefore, soaps are not used for washing clothes when the water is hard.