Question

Which of the following electrolytes is least effective in causing the flocculation of positively charged ferric hydroxide sol?

Options

• K₃[Fe(CN)₆]

• K₂CrO₄

• K₄[Fe(CN)₆]

• KBr

Answer 1

KBr

Explanation:

This is because the coagulating power depends on the charge of the oppositely charged ions; KBr provides Br⁻ ions, which have a much higher flocculation value (i.e., lower coagulating power) compared to complex ions like [Fe(CN)₆]⁴⁻ or \[\ce{CrO^{2-}4}\] that have higher charges and thus greater coagulating power. Hence, KBr is least effective in flocculating positively charged Fe(OH)₃ sol.