Question

Which one of the following forms micelles in aqueous solution above certain concentration?

• A. Urea
• B. Dodecyl trimethyl ammonium chloride
• C. Pyridinium chloride
• D. Glucose

Answer 1

The Correct Option is B

In this question, we need to identify which of the given substances forms micelles in an aqueous solution above a certain concentration. Understanding the concept of micelles is crucial to answering this question correctly.

Micelles are aggregates of surfactant molecules dispersed in a liquid colloid. A micelle is a structure that forms when the concentration of surfactant molecules in a solution exceeds a critical concentration, known as the critical micelle concentration (CMC). At this concentration, the surfactant molecules spontaneously assemble into spherical structures with hydrophobic tails directed inward and hydrophilic heads facing outward.

Among the options given:

1. Urea: Urea does not form micelles. It is a simple organic compound that acts as neither a surfactant nor an amphiphilic molecule.
2. Dodecyl trimethyl ammonium chloride: This is a cationic surfactant. Surfactants are compounds that lower the surface tension between two liquids or a liquid and a solid. They are typically amphiphilic, containing both hydrophilic and hydrophobic parts. Above a critical micelle concentration, such surfactants form micelles in aqueous solutions. Thus, dodecyl trimethyl ammonium chloride is the correct answer.
3. Pyridinium chloride: While it is a salt, it doesn't typically act as a surfactant or form micelles.
4. Glucose: Glucose is a simple sugar, and like urea, does not have the amphiphilic nature required to form micelles.

In conclusion, dodecyl trimethyl ammonium chloride is a prime example of a cationic surfactant that can form micelles above a critical micelle concentration in an aqueous solution.