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

The four statements given in the question deal with the fundamental properties of colloidal systems. We examine each one.

Statement (I) Lyophobic (solvent-hating) colloids cannot be prepared by simply mixing the dispersed phase with the dispersion medium.
Lyophobic particles have little affinity for the medium; therefore, special techniques such as electrical dispersion, ultrasonic dispersion or peptisation are required to break the bulk substance into colloidal-sized particles. Hence Statement (I) is true.

Statement (II) In an emulsion the dispersed phase as well as the dispersion medium are liquids.
Typical examples are milk (liquid fat dispersed in water) and cold cream (water dispersed in oil). By definition this is correct, so Statement (II) is true.

Statement (III) Micelles form whenever a surfactant is dissolved in any solvent at any temperature.
Micelle formation actually requires
  • a polar solvent, usually water,
  • surfactant concentration ≥ the critical micelle concentration (CMC), and
  • temperature ≥ the Kraft temperature.
If these conditions are not met, surfactant molecules remain as individual ions or molecules. Therefore Statement (III) is false.

Statement (IV) Tyndall effect is observed even when the dispersed phase and the dispersion medium have identical refractive indices.
The Tyndall effect (scattering of light by colloidal particles) becomes prominent only when there is a significant difference between the refractive indices of the two phases. If the indices are identical, scattering is negligible and the beam is invisible. Hence Statement (IV) is false.

Only Statements (I) and (II) are correct. Therefore, the correct choice is:

Option A which is: (I) and (II)