Question

Which of the following electrolytes is the most effective for the coagulation of Fe(OH)₃ sol which is a positively charged sol ?
NaCl, Na₂SO₄, Na₃PO₄

Answer 1

NACl and na2so4. conduct electricity in positively charged solution

Answer 2

In colloidal chemistry,the coagulation capacity of different electrolytes are different. It depends upon the charge of the active ion are called flocculating ion.It can be defined as the ion  which is  carrying charge opposite to the charge on the colloidal particles.

According to Hardy schulze rule,the coagulation power of precipitated ion is more if its valency is high.Fe(OH)₃ sol a  positively charged sol.Among NaCl, Na₂SO₄, Na₃PO₄. the valency of chloride. sulfate and phosphate is 1,2,3 respectively.

        Hence Na₃PO₄ is most effective electrolyte for the coagulation of Fe(OH)₃ sol which is a positively charged sol.