Question

The protecting power of lyophilic colloidal sol is expressed in terms of

• A. coagulation value
• B. gold number
• C. critical micelle concentration
• D. oxidation number

Answer 1

The Correct Option is B

The question pertains to colloidal chemistry, specifically the concept of the stabilizing ability of lyophilic (solvent-loving) colloids. The protecting power of lyophilic colloids is quantitatively expressed by the gold number.

Let's explore each option to understand why the correct answer is the gold number:

1. Coagulation Value: This term refers to the concentration of an electrolyte required to cause the coagulation of a colloid. It is not related to the protective action of lyophilic colloids but rather to the process of destabilizing colloids.
2. Gold Number: This is the correct answer. The gold number is a measure of the protective ability of a lyophilic colloid to prevent the precipitation of a lyophobic colloid when an electrolyte is added. It is defined as the minimum amount (in milligrams) of a lyophilic colloid that prevents the coagulation of 10 mL of a gold sol by 1 mL of a 10% sodium chloride solution. A lower gold number indicates greater protective power.
3. Critical Micelle Concentration: This term is used in the context of surfactants and micelles, referring to the concentration at which micelles begin to form. It is not related to the protecting power of colloids.
4. Oxidation Number: This term indicates the degree of oxidation of an atom in a chemical compound and is unrelated to colloidal stability or protecting power.

Thus, the ability of a lyophilic colloid to protect a lyophobic colloidal dispersion from coagulation is best expressed by the gold number. This concept is crucial in the stabilization of colloids in various applications in chemistry and materials science.