Question

Which of the following surfactants is an ANIONIC surfactant?

• A. Lecithin
• B. Sorbitan esters
• C. Benzalkonium chloride
• D. Soaps

Answer 1

The Correct Option is D

Anionic surfactants are a type of surface-active agents that carry a negative charge. They are commonly used in detergents and cleaning products due to their excellent ability to remove dirt and oils. Let's evaluate the given options to determine which one is an anionic surfactant:

1. Lecithin: Lecithin is a phospholipid and typically acts as a non-ionic surfactant. It does not carry any specific charge, hence it is not an anionic surfactant.
2. Sorbitan esters: Sorbitan esters, commonly referred to as Span, are non-ionic surfactants. They do not possess an ionic charge, making them unsuitable as anionic surfactants.
3. Benzalkonium chloride: This is a cationic surfactant, which means it carries a positive charge. Therefore, it is not an anionic surfactant.
4. Soaps: Soaps are the salts of fatty acids, typically in the form of sodium or potassium salts. In aqueous solutions, they dissociate into negative ions (such as RCOO^-) and positive ions (such as Na⁺). The presence of these negatively charged ions categorizes soaps as anionic surfactants.

Based on the above evaluations, the correct answer is Soaps, as they are the only option that acts as an anionic surfactant by carrying a negative charge in a solution.