One or more options correct
Correct statement(s) about colloids and adsorption is(are)
- A. For a positively charged sol, has a lower coagulation value than
- B. Physical adsorption of a gas on a solid is endothermic, so it increases with increase in temperature
- C. Micelles form from soap solutions at any temperature once the concentration exceeds the CMC
- D. Milk is an emulsion in which water is the dispersed phase and fat is the dispersion medium
Show answer and solution
Answer: A
Option A is correct: a positive sol is coagulated by the anion of the electrolyte (Hardy-Schulze rule), and the trivalent is far more effective than the monovalent , so its coagulation value (minimum concentration needed) is lower. Option B is wrong: adsorption lowers the surface free energy and the entropy of the gas, so it is exothermic and decreases with rising temperature (Le Chatelier). Option C is wrong: micelle formation requires the concentration to exceed the CMC and the temperature to exceed the Krafft temperature; below it the surfactant is not soluble enough. Option D is wrong: in milk fat droplets are dispersed in water, so it is an oil-in-water emulsion with water as the medium.
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