Question

Both soap and detergent are some type of salts. What is the difference between them? Describe in brief the cleansing action of soap. Why do soaps not form lather in hard water? List two problems that arise due to the use of detergents instead of soaps.

Answer 1

1. Most soap is made from natural ingredients such as coconut oil and potassium hydroxide. Detergents often contain synthetic ingredients such as dyes, sodium laureth sulfate, disodium phosphate and fragrances.

2. Most of the dirt is oily in nature and oil does not dissolve in water. The molecule of soap constitutes sodium or potassium salts of long-chain carboxylic acids. In the case of soaps, the carbon chain dissolves in oil and the ionic end dissolves in water. Thus the soap molecules form structures called micelles. In micelles, one end is towards the oil droplet and the other end which is the ionic faces outside. Therefore, it forms an emulsion in water and helps in dissolving the dirt when we wash our clothes.

3. When soap is mixed with hard water, the calcium and magnesium salts displaces the salts of sodium and potassium present in the soap and forms scum which is not soluble. Hence soaps are not effective in hard water for washing clothes.

4. Demerits: a. Detergents are non-biodegradable.

b. Detergents are harsh on skin as compared to soap.