On the basis of Hardy-Schulze rule explain why the coagulating power of phosphate is higher than chloride.

The coagulation property of the electrolyte depend upon the valency of the coagulating ion and hence if the valency of the ion is greater than it possess more coagulating power. The ion which is responsible for the coagulation of the colloidal particle has charge opposite to that of the colloidal particles.

Therefore the coagulating power of the negatively charged anions towards the coagulation of positively charged sols is as shown below:

PO₄^-3 > SO₄^-2 > Cl^-

Therefore the charge present on the chloride ion is less as compared to that of the charge present on the phosphate ion and hence the PO₄^-3 possess greater coagulating property as compared to the chloride ion.