Ferric hydroxide sol is positively charged colloid. The coagulating power of `NO_(3)^(-)`, `SO_(4)^(2-)` and `PO_(4)^(3-)` ions would be in the order

Options

A. `NO_(3)^(-) gt SO_(4)^(2-) gt PO_(4)^(3-)`
B. `SO_(4)^(2-) gt NO_(3)^(-) gt PO_(4)^(3-)`
C. `PO_(4)^(3-)gtSO_(4)^(2-)gtNO_(3)^(-)`
D. `NO_(3)^(-) = SO_(4)^(2-) = PO_(4)^(3-)`

Answer

C

Explanation

According to Hardy - Schulze rule the ions having opposite charge to sol particle cause coagulation and greater the valency of oppositely charged ion more is the coagulating power `(PO_(4)^(3-) gt SO_(4)^(2-) gt NO_(3)^(-)`).