Question

Which one of the following is most effective in causing the coagulation of an ${As}_2{S}_3$ sol?

• A. $KCl$
• B. $Al{Cl}_3$
• C. $Mg{SO}_4$
• D. $K_{3}Fe{\left(CN\right)}_6$

Answer 1

The correct option is B $Al{Cl}_3$

According To Hardy-Schulze rule, the coagulating power of the active ion increases with the valency of the active ion, the coagulating power of the active ion increases with the valency of the active ion. The coagulating power of $A{l}^{3+}$ is highest due to high charge and small size, therefore, aluminium chloride will be required in minimum amount to coagulate negatively charged sol of $A{s}_2{S}_3$