Question

Detergents do not give scum with hard water because they have:

• A. ammonium salts of long chain carboxylic acids.
• B. sulphonate salts of long chain carboxylic acids.
• C. both A and B
• D. none of these

Answer 1

The correct option is C both A and B

Soaps are not suitable to be used for washing clothes with hard water. Calcium and magnesium ions present in hard water combine with the soap, forming insoluble sticky grey precipitate called scum. This results in the wastage of soap. Detergents are generally ammonium or sulphonate salts of long chain carboxylic acids. They do not make scum in hard water as these chains do not react with metal ions to form insoluble precipitate.