Question
What are lyophilic and lyophobic sols? Give one example of each type. Why are hydrophobic sols easily coagulated?
Solution
Answer:
On the basis of attraction between dispersed phase and dispersion medium colloids may be classified into lyophillic sol and lyophobic sol.
If dispersed phase (solid) tends to attract (i.e., like or love) dispersion medium (liquid), the resultant sol is termed as lyophilic sol. Examples are: Sol of gum, gelatine, starch etc. are lyophilic sols.
On the other hand if dispersed phase tends to repel (i.e., dislike or hatred) dispersion medium, the resultant sol is termed as lyophobic sol. Examples are: Sols of metals, metal hydroxides, metal sulphides etc. are lyophobic sols.
Hydrophobic sols easily coagulated as in this dispersion medium has no apparent affinity or interaction with the dispersed phase.
