Chemistry - Surface Chemistry Question with Solution | TestHub
Which of the following statement is incorrect:
Options:
Answer:
Solution:
Explanation:
A. Hardy-Schulze rule states that the coagulating power of an electrolyte is directly proportional to the fourth power of the valency of the effective ion. For a positively charged sol like Fe(OH)₃, the effective ions are anions. The valency of [Fe(CN)₆]³⁻ is 3, and for CrO₄²⁻ is 2. Thus, [Fe(CN)₆]³⁻ has higher coagulating power and a lower coagulation value than CrO₄²⁻. This statement is correct.
B. Latex is a natural rubber dispersion, which is a colloidal sol of negatively charged rubber particles stabilized by proteins. This statement is correct.
C. As₂S₃ sol is negatively charged. In electro-osmosis, the dispersion medium moves towards the electrode that has the same charge as the colloidal particles to maintain electrical neutrality. Therefore, the dispersion medium of As₂S₃ sol (negatively charged particles) would move towards the cathode, not the anode. This statement is incorrect.
D. When ferric chloride (FeCl₃) is added to excess NaOH, Fe(OH)₃ is formed. If FeCl₃ is in excess, a positively charged sol is obtained. If NaOH is in excess, a negatively charged sol of Fe(OH)₃ is obtained due to adsorption of OH⁻ ions. This statement is correct.