Exams › JEE Advanced › Chemistry

A sol has positively charged colloidal particles. Which of the following electrolytes requires the lowest concentration to cause coagulation?

1. NaCl
2. K4[Fe(CN)6]
3. ZnCl2
4. Na2SO4

Correct answer: K4[Fe(CN)6]

Solution

For a positively charged sol, anions act as coagulating ions. Hardy-Schulze rule: coagulating power proportional to (charge)⁶ approximately, so even modest charge differences matter greatly. Anion charges: NaCl gives Cl⁻ (z=1), Na2SO4 gives SO4²- (z=2), ZnCl2 gives Cl⁻ (z=1), K4[Fe(CN)6] gives [Fe(CN)6]⁴- (z=4). Highest anion charge = [Fe(CN)6]⁴-, so K4[Fe(CN)6] has highest coagulating power and needs the lowest concentration.

Related JEE Advanced Chemistry questions

• Methylene blue, from its aqueous solution, is adsorbed on activated charcoal at 25°C. For this process, the correct statement is -
• Which of the following statements about colloids is accurate?
• Soap removes grease stains from fabric primarily by which mechanism?
• According to the Freundlich adsorption isotherm, which of the following relationships between the extent of adsorption (x/m) and pressure (p) is correct?
• A colloid formed by dispersing a liquid in another liquid is called:
• Which of the following statements correctly describes the properties of hydrophilic sols?

⚔️ Practice JEE Advanced Chemistry free + battle 1v1 →