Question

(i) Differentiate between adsorption and absorption.
(ii) Out of $Mg{Cl}_2$ and $Al{Cl}_3$, which one is more effective in causing coagulation of negatively charged sol and why?
(iii) Out of sulphur sol and proteins, which one forms multimolecular colloids?

Answer 1

(i) Absorption is the process in which a fluid is dissolved by a liquid or a solid (absorbent). Adsorption is the process in which atoms, ions or molecules from a substance (it could be gas, liquid or dissolved solid) adhere to a surface of the adsorbent. Adsorption is a surface-based process where a film of adsorbate is created on the surface while absorption involves the entire volume of the absorbing substance.

(ii) According to Hardy Schulze rule, $AlC{l}_3$ with high positive charged cation $\left(A{l}^{3+}\right)$ will coagulate more effectively than $MgC{l}_2$. Effectiveness of the salt in causing flocculation depends on the charge of the ion. Trivalent ions are much more effective than divalent ions as according to the Hardy – Schultz Law, “Greater the valency of oppositely charged ions of the electrolyte being added, the faster is coagulation”.

(iii) Sulphur sol form multimolecular colloids. Multimolecular Colloids are in which large number of atoms or smaller molecules of a substance on dissoluton aggregate together to form species having size in the colloidal range (diameter <1 nm). Aa sulphur sol consists of particles containing a thousand or more of $s_8$ sulphur molecules. Proteins have large molecular masses and called Macromolecular colloids.