Answer: The calcium and magnesium salts of detergents remain soluble in water, unlike the corresponding soap salts.
- A Detergents are generally stronger acids than ordinary soaps in solution under most conditions encountered
- B The calcium and magnesium salts of detergents remain soluble in water, unlike the corresponding soap salts
- C Detergents are said to lack any hydrophobic tail in their molecular structure as frequently observed in practice
- D Hard water is said to have no chemical effect on either soaps or detergents in many documented cases
Correct answer: B. The calcium and magnesium salts of detergents remain soluble in water, unlike the corresponding soap salts
Explanation: Soaps form an insoluble precipitate (scum) with Ca<sup>2+</sup>/Mg<sup>2+</sup> in hard water. Synthetic detergents' calcium and magnesium salts remain soluble, so they continue to clean effectively in hard water.
The hydrophobic hydrocarbon tail of each soap/detergent molecule dissolves into an oily dirt droplet, while the hydrophilic (ionic) head stays in the surrounding water - trapping the grease inside a micelle that rinses away with water.
Concept context
Drugs and how they interact with biological targets, chemicals in food, and cleansing agents (soaps and detergents) - chemistry applied directly to daily life and healthcare.