Question

Which aqueous solution of concentration 0.01 M salt i.e., KCl, MgCl₂ and AlCl₃ would be most effective in coagulating a negatively charged colloidal solution of As₂S₃?

Answer 1

The most effective aqueous solution for coagulating a negatively charged colloidal solution of As₂S₃ among 0.01 M KCl, MgCl₂ and AlCl₃ is AlCl₃. This is because the coagulating power follows the order based on the cation charge: Al³⁺ > Mg²⁺ > K⁺, and a higher valency ion causes faster coagulation. Thus, AlCl₃ with Al³⁺ ions is most effective in the coagulation of the negative sol of As₂S₃.