Question

The capacity to bring about coagulation of a sol increases with:

• A. Mobility of ion
• B. Atomic radii of ion
• C. Valency of ion
• D. Size of an ion

Answer 1

The correct option is C Valency of ion

The amount of electrolyte required to coagulate a fixed amount of a sol depends upon valency of flocculating ion.

Hardy-Schulze Rule:
Greater the valence of flocculating ion added, greater is its power to cause coagulation.

Coagulating power of bivalent ion is 20-80 times higher than monovalent ion. Coagulating power of trivalent ion is many more times higher than divalent ion.

Order of coagulating power of anion for positively charged sol:
$\left[Fe\right(C{N}_6){]}^{4-}>P{O}_4^{3-}>S{O}_4^{2-}>C{l}^{-}$

Order of coagulating power of cation for negatively charged sol:
$A{l}^{3+}>B{a}^{2+}>N{a}^{+}$