Out of BaCl₂ and KCl, which is more effective in causing coagulation of a negatively charged colloidal sol? Give reason.

BaCl₂ is more effective in causing coagulation of a negatively charged colloidal sol. According to Hardy-Schulze rule greater the charge on the flocculating ion greater is its ability to coagulate. Here we need to coagulate a negatively charged ion, i.e., positively charged ions are required. Out of barium and potassium(K), barium exhibits a valence of +2 while potassium has a valance of +1, as barium has greater charge it is more effective then potassium.