Question

The electrolyte having maximum flocculation value for $AgI/Ag^+$ sol is

• A. $NaCl$
• B. $Na_2S$
• C. $Na_2SO_4$
• D. $Na_3PO_4$

Answer 1

Answer: (A)

$NaCl$

Answer 2

According to Hardy - Schulze rule

Flocculation value $(FV) \propto \frac{1}{\text { Coagulation power }}$

Coagulation value

Since, coagulating power is direct us related to the valencies of coagulating ion.

Thus,

$F V \propto \frac{1}{\text { valency of flocculating ion electrolyte }}$

Hence, greater the valency of coagulating ion, lower will be the flocculating value and vice versa.

As for the given positively charged sol, negative ion would be required for coagulation thus, for the given anions the coagulation power will be

$PO _{4}^{3-}< SO _{4}^{2-}= S ^{2-}< Cl ^{-}$ or flocculating but coagulating value would be in an order of :

$Cl ^{-}> S ^{2-}= SO _{4}^{2-}> PO _{4}^{3-}$

Hence, $NaCl$ will have the maximum flocculating value for the given positively charged sol.