What are lyophilic and lyophobic sols ? Give one example of each type. Which one of these two types of sols is easily coagulated and why?

Explanation

(i) Lyophilic sols : The colloids in which the particles of the dispersed phase have a strong affinity for the dispersion medium are called lyophilic sols. These colloidal solutions, even if precipitated, change back to the colloidal form simply by adding dispersion medium. So lyophilic sols are reversible in nature e.g., glue, starch, rubber, etc.
(ii) Lyophobic sols : The colloids in which particles of the dispersed phase have no or very little affinity for dispersion medium are called lyophobic sols. These are irreversible in nature i.e., once precipitated, they have little tendency to get back into the colloidal form on simply adding dispersion medium e.g., `As_(2)S_(3)` sol.
Lyophobic sols need stabilising agents for their preservation.
Hydrophobic solutions get easily coagulated on the addition of a small amount of electrolytes or by heating or even shaking as they are not stable.