Which of the following exhibits the minimum coagulating power for precipitating of positively charged ferric oxide sol ?

Step-by-step solution

According to the Hardy-Schulze rule, the coagulating power of an ion is directly proportional to the magnitude of its charge. Since the ferric oxide sol is positively charged, the anions of the added electrolyte are responsible for its coagulation. The anions provided by the given electrolytes are: KNO ₃ NO ₃⁻ (charge magnitude = 1 ) K ₂ SO ₄ SO ₄²⁻ (charge magnitude = 2 ) K ₃ PO ₄ PO ₄³⁻ (charge magnitude = 3 ) K ₄[ Fe(CN) ₆] [ Fe(CN) ₆]⁴⁻ (charge magnitude = 4 ) The order of coagulating power is [ Fe(CN) ₆]⁴⁻ > P