Question

which of the following electrolytes is most effective for the coagulation of Fe(OH)3 sol and why?

NaCl,Na2SO4,Na3PO4

Answer 1

Answer: $Na_3PO_4$

Explanation: $Fe(OH)_3$ sol is positively charged. In order to bring about the coagulation oppositely charged ions must be added.

According to Hardy Schulze rule, greater the charge on the oppositely charged ion of the electrolyte added, more effective is the coagulation. Thus to coagulate a positively charged colloid, we must see the negatively charged ions.

$NaCl$ contains $Cl^{-}$ ions, $Na_2SO_4$ contains $SO_4^{2-}$ ions and $Na_3PO_4$ contains $PO_4^{3-}$ ions.

Thus ions bearing the highest negative charge i.e. $PO_4^{3-}$ ions will be more effective in bringing the coagulation of positively charged $Fe(OH)_3$ sol.

Answer 2

Answer:

Na3PO4

Explanation:

Fe(OH)3 is a positively charged sol. So, for coagulating it we need a negatively charged sol.

As per Hardy Schulze rule, greater the charge on the oppositely charged ion of the electrolyte added, more effective is the coagulation. Thus to coagulate a positively charged colloid, we must see the negatively charged ions.

so, Na3PO4 has Na³- (highest negative power among the given options)

Hence, Answer is Na3PO4

Hope it helps....