Question

For the coagulation of positively charged hydrated ferric-oxide sol, the flocculating power of the ions is in the order :

• A. \(PO_4^{3-}\gt SO_4^{2-}\gt Cl^{-}\gt[Fe(CN)_6]^{4-}\)
• B. \(Cl^{-}\gt SO_4^{2-}\gt PO_4^{3-}\gt[Fe(CN)_6]^{4-}\)
• C. \(SO_4^{2-}= Cl^{-}= PO_4^{3-}=[Fe(CN)_6]^{4-}\)
• D. \([Fe(CN)_6]^{4-}\gt PO_4^{3-}\gt SO_4^{2-}\gt Cl^{-}\)

Answer 1

The Correct Option is D

Flocculation depends on the charge density of the ions. The ions with higher charge density are more effective in neutralizing the charge of the sol particles, causing coagulation. Here's the order based on their flocculating power:

• \( \text{Fe(CN)}_6^{4-} \): This ion has a high charge and small size, making it the most effective flocculating ion.
• \( \text{PO}_4^{3-} \): Phosphate ions are effective but less so than \( \text{Fe(CN)}_6^{4-} \).
• \( \text{SO}_4^{2-} \): Sulfate ions have a lower charge density than phosphate ions, thus they are less effective in flocculation.
• \( \text{Cl}^- \): Chloride ions have the lowest charge density and are the least effective in flocculation.

Thus, the correct order of flocculating power is:

\[ \text{Fe(CN)}_6^{4-} > \text{PO}_4^{3-} > \text{SO}_4^{2-} > \text{Cl}^- \]

Therefore, the correct answer is (D).