The correct statement(s) related to colloids is(are)
- (A)The process of precipitating colloidal sol by an electrolyte is called peptization.
- (B)Colloidal solution freezes at higher temperature than the true solution at the same concentration.✓ Correct
- (C)Surfactants form micelle above critical micelle concentration (CMC). CMC depends on temperature✓ Correct
- (D)Micelles are macromolecular colloids.
Answer: (B), (C)
Solution
(A) FALSE: The process of precipitating colloidal sol by an electrolyte is called coagulation or flocculation, not peptization. Peptization is the reverse process - dispersion of a precipitate into a colloidal sol.
(B) TRUE: Colloidal solutions have very large molar masses, so their molal concentration is very small even at the same mass concentration. This means colligative properties (including freezing point depression) are much smaller. Therefore, ΔT_f is smaller and the solution freezes at a higher temperature than a true solution.
(C) TRUE: Surfactants form micelles above the critical micelle concentration (CMC). The CMC value depends on temperature, as well as other factors like the nature of the surfactant and presence of electrolytes.
(D) FALSE: Micelles and macromolecular colloids are two different types of colloids. Micelles are association colloids formed by aggregation of small molecules, while macromolecular colloids consist of large molecules themselves.
(B) TRUE: Colloidal solutions have very large molar masses, so their molal concentration is very small even at the same mass concentration. This means colligative properties (including freezing point depression) are much smaller. Therefore, ΔT_f is smaller and the solution freezes at a higher temperature than a true solution.
(C) TRUE: Surfactants form micelles above the critical micelle concentration (CMC). The CMC value depends on temperature, as well as other factors like the nature of the surfactant and presence of electrolytes.
(D) FALSE: Micelles and macromolecular colloids are two different types of colloids. Micelles are association colloids formed by aggregation of small molecules, while macromolecular colloids consist of large molecules themselves.
JEE Advanced · 2021 · 03 Oct 2021 · Paper 1 · One or more correct options