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
- A
(I) and (II)
- B
(II) and (III)
- C
(III) and (IV)
- D
(II) and (IV)
(I) Correct. In a lyophobic colloid there is little affinity between the dispersed phase and the medium, so simple mixing does not yield a stable sol. Special methods (Bredig arc, peptisation, chemical precipitation) are required.
(II) Correct. Emulsions are colloidal systems of one liquid dispersed in another liquid (for example oil in water).
(III) Incorrect. Micelle formation requires a specific surfactant-solvent combination, a concentration above the CMC, and a temperature above the Krafft temperature. It does not occur in any solvent at any temperature.
(IV) Incorrect. The Tyndall effect arises from scattering of light, which needs a significant difference in refractive index between the dispersed phase and the medium. If the two refractive indices are equal, no scattering is seen.
Therefore statements (I) and (II) are correct, option (A).