Which of the following statements about soaps and detergents is correct regarding their action in hard water?
Correct: B
Hard water contains dissolved salts of calcium and magnesium. Soaps (sodium or potassium salts of long-chain fatty acids) react with these metal ions to form insoluble precipitates called scum, which reduces their cleansing action. Detergents (sodium salts of long-chain benzene sulphonic acids or alkyl hydrogen sulphates) do not form insoluble precipitates with calcium and magnesium ions and thus work effectively in hard water.