Which of the following ions has the least flocculating power?

Options

A. `Cl^(-)`
B. `SO_(4)^(2-)`
C. `PO_(4)^(3-)`
D. `[F(CN)_(6)]^(4-)`

Answer

A

Explanation

Generally, the greater the valence of the flocculating ion added, the greater is its power to cause precipitation. This is known as Hardy-Schulze rule. In the coagulation of a negative sol, the flocculating power is in the order:
`Al^(3+)gtBa^(2+)gtNa^(+)` . Similarly, in the coagulation of a positive sol, the flocculating power is in the order: `[Fe(CN)_(6)]^(4-)gtPO_(4)^(3-)gtSO_(4)^(2-)gtCl^(-)`