Question

Which of the following is more effective in coagulating positively charged hydrated ferric oxide sol : (i) KCl (ii) CaSO4 (iii) K3 [Fe(CN)6 ].

Answer 1

I think CaSO4 is the answer

Answer 2

OPTION (iii) is correct
The higher the valency of the coagulating ion, greater the coagulating power of the ion, since the sol if iron hydroxide is positively charged sol, so the negative ion will coagulate the sol. so, out the given electrolytes ferrocyanide has the highest magnitude of negative charge:

Cl-<SO42-<[Fe(CN)6]-4.

Therefore, it will have the highest coagulating power.
Hope u got it..:)