Which of the following electrolytes will have maximum coagulating value for AgI/Ag⁺ sol?

According to Hardy-Schulze rule, greater the charge of the flocculating ion, greater is its ability to bring coagulation.

Here, in all of these, cation Na⁺ has equal charge = +1.

In (i), the anion is S^2-

In (ii), the anion is PO₄^3-.

In (iii), the anion is SO₄^2-

In (iv), the anion is Cl^-.

So highest charge of anion in option (ii). So (ii) is the correct option.

(i), (ii) and (iv) wrong according to Hardy-Schulze rule.