In a colloidal state the particle size of the dispersed phase range between 103 to 106 pm and colloidal sol is heterogeneous in nature. Based on the nature of interaction between the dispersed phase and dispersion medium colloidal sol are classified as lyophilic and lyophobic. Stability of sol is due to presence of charge on the sol particles and the neutralisation of the same is known as coagulation or precipitation.
Based on this answer the following.
Lyophilic sols are more stable than lyophobic sols because
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → The colloidal particles are solvated
A lyophobic sol owes its stability only to the charge on its particles; once the charge is neutralised (say by an electrolyte) it coagulates. Lyophilic colloids have a second stabilising factor: they are extensively solvated, i.e. each particle is covered by a sheath of the liquid in which it is dispersed. To coagulate them both the charge and the solvent layer must be removed, which is why lyophilic sols are more stable.
Why the other options are incorrect
Option (1) The colloidal particles have positive charge — Incorrect. Charge stabilises both kinds of sol, and particles of either kind may be positive or negative; this does not make lyophilic sols more stable.
Option (2) The colloidal particles have no charge — Incorrect. Lyophilic particles do carry charge; uncharged particles would be less stable, not more.
Option (4) A small amount of electrolyte is added to stabilise — Incorrect. This describes peptization (making a sol from a precipitate) and applies to lyophobic sols; it is not why lyophilic sols are more stable.
Note: This question is from the pre-rationalised NCERT book (2022-23). The topic is not there in the latest NCERT book (2026-27), and it is also out of the CUET 2026 syllabus.
NCERT (Pre-rationalised edition, 2022-23):
Protection of Colloids
