Question

Out of MgCl₂ and AlCl₃, which one is more effective in causing coagulation of negatively charged sol and why?

Answer 1

According to the Schulze-Hardy rule, the effectiveness of the salt causing flocculation depends on the charge on the ion of opposite sign to the charge on the sol particles. The greater the magnitude of the opposite charge, the higher the ability of a salt to coagulate the sol.

Thus, trivalent salt AlCl₃ is more effective in causing the coagulation of a negatively charged sol than divalent salt MgCl₂.