2022 Surface ChemistryColloids – Coagulation and Hardy-Schulze Rule Medium Question 4 of 30 in Surface Chemistry

Given below are two statements: Statement I: In the coagulation of negative sol, the flocculating power of the three given ions is in the order- $Al^{3+}>Ba^{2+}>Na^+$ Statement II: In the coagulation of positive sol, the flocculating power of the three salts is in the order- $NaCl>Na_2SO_4>Na_3PO_4$ In the light of the above statements, choose the most appropriate answer from the options given below:

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

The answer is D.

Solution

According to the Hardy-Schulze rule, the greater the valence of the flocculating ion, the greater its coagulating power. Statement I: for a negative sol, cations are effective: $Al^{3+} > Ba^{2+} > Na^+$ – correct. Statement II: for a positive sol, anions are effective: $PO_4^{3-} > SO_4^{2-} > Cl^-$, i.e. $Na_3PO_4 > Na_2SO_4 > NaCl$ – so the given order is incorrect. So Statement I is correct but Statement II is incorrect.

Concept flocculating power of ions

Surface Chemistry in past papers

30 questions from this chapter have appeared across 20 exam years.