Consider the following statements related to colloids.
(I) Lyophobic colloids are not formed by simple mixing of dispersed phase and dispersion medium.
(II) For emulsions, both the dispersed phase and the dispersion medium are liquid.
(III) Micelles are produced by dissolving a surfactant in any solvent at any temperature.
(IV) Tyndall effect can be observed from a colloidal solution with dispersed phase having the same refractive index as that of the dispersion medium.
The option with the correct set of statements is
(I) Lyophobic colloids are not formed by simple mixing of dispersed phase and dispersion medium.
(II) For emulsions, both the dispersed phase and the dispersion medium are liquid.
(III) Micelles are produced by dissolving a surfactant in any solvent at any temperature.
(IV) Tyndall effect can be observed from a colloidal solution with dispersed phase having the same refractive index as that of the dispersion medium.
The option with the correct set of statements is
- (A)(I) and (II)✓ Correct
- (B)(II) and (III)
- (C)(III) and (IV)
- (D)(II) and (IV)
Answer: (A)
Solution
Statement (I) is correct: Lyophobic colloids have no affinity between dispersed phase and dispersion medium, so special methods (like electrical dispersion or peptization) are required for their preparation—simple mixing does not work.
Statement (II) is correct: Emulsions are by definition liquid-in-liquid colloidal systems.
Statement (III) is incorrect: Micelles form only above a critical micelle concentration (CMC) and above the Kraft temperature, not at any temperature.
Statement (IV) is incorrect: The Tyndall effect requires a significant difference in refractive index between the dispersed phase and dispersion medium to cause light scattering. If they have the same refractive index, no scattering occurs.
Therefore, statements (I) and (II) are correct.
Statement (II) is correct: Emulsions are by definition liquid-in-liquid colloidal systems.
Statement (III) is incorrect: Micelles form only above a critical micelle concentration (CMC) and above the Kraft temperature, not at any temperature.
Statement (IV) is incorrect: The Tyndall effect requires a significant difference in refractive index between the dispersed phase and dispersion medium to cause light scattering. If they have the same refractive index, no scattering occurs.
Therefore, statements (I) and (II) are correct.
JEE Advanced · 2023 · 04 Jun 2023 · Paper 2 · Single correct option