Question

The temperature at which the solubility of the surfactant is equal to the CMC, is called as

• A. Critical micellar concentration
• B. Kraft point
• C. Cloud point
• D. Solubilization

Answer 1

The Correct Option is B

The question asks for the term used to describe the temperature at which the solubility of a surfactant equals its critical micelle concentration (CMC). Let's analyze the options provided:

1. Critical micellar concentration (CMC): This is the concentration of surfactants above which micelles form and all additional surfactants added to the system form micelles. It is a concentration term, not a temperature.
2. Kraft point: This is indeed the correct term. The Kraft point is the temperature at which the solubility of a surfactant in water is equal to its CMC. Below this temperature, surfactants typically exist in an insoluble crystalline form, while above it, they dissolve to form micelles.
3. Cloud point: This term is used for nonionic surfactants, and it refers to the temperature at which a solution becomes cloudy due to phase separation. It is different from the Kraft point.
4. Solubilization: This is a process where a solute (e.g., oil) is dissolved into the micelles of a surfactant in a solvent (usually water). It is not directly related to temperature and solubility relation as described in the question.

Based on the explanations, the correct answer is the Kraft point. It specifies the exact condition of temperature where the surfactant achieves solubility equivalent to its critical micelle concentration, allowing micelle formation to occur freely.