Question

Statement I: In the coagulation of a negative sol, the flocculating power of the three given ions is in the order - Al³⁺ > Ba²⁺ > Na⁺
Statement II: In the coagulation of a positive sol, the flocculating power of the three given salts is in the order - NaCl > Na₂SO₄ > Na₃PO₄
Choose the most appropriate answer from the options given below:

• A. Both Statement I and Statement II are correct.
• B. Both Statement I and Statement II are incorrect.
• C. Statement I is correct but Statement II is incorrect.
• D. Statement I is incorrect but Statement II is correct.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
According to the Hardy-Schulze Rule, the coagulation (flocculation) power of an electrolyte depends on the valency of the ion carrying a charge opposite to that of the sol particles. Higher the valency, greater is the power.
Step 2: Detailed Explanation:
Analysis of Statement I:
To coagulate a negative sol, we need positive ions (cations).
The given cations are \(Al^{3+}\), \(Ba^{2+}\), and \(Na^+\).
Since the valency order is \(3>2>1\), the flocculating power follows: \(Al^{3+}>Ba^{2+}>Na^+\).
Thus, Statement I is correct.

Analysis of Statement II:
To coagulate a positive sol, we need negative ions (anions).
The anions provided by the salts are \(Cl^-\) (from \(NaCl\)), \(SO_4^{2-}\) (from \(Na_2SO_4\)), and \(PO_4^{3-}\) (from \(Na_3PO_4\)).
The valency order of anions is \(PO_4^{3-}>SO_4^{2-}>Cl^-\).
Therefore, the power order should be \(Na_3PO_4>Na_2SO_4>NaCl\).
The statement gives the reverse order. Thus, Statement II is incorrect.
Step 3: Final Answer:
Statement I is correct and Statement II is incorrect.