Question

State Hardy–Schulze law.

Hint:

Valency matters! Multivalent ions coagulate colloids much faster than monovalent ions.

Answer 1

Step 1: Nature of colloidal particles.
Colloidal particles carry either a positive or negative charge. Their stability depends on the repulsion between similarly charged particles.
Step 2: Role of oppositely charged ions.
When oppositely charged ions are added, they neutralize the charge on the colloidal particles and cause coagulation.
Step 3: Order of coagulating power.
For negatively charged sols: Al\(^ {3+}\)>Ba\(^ {2+}\)>Na\(^+\). For positively charged sols: [Fe(CN)\(_6\)]\(^{4-}\)>PO\(_4^{3-}\)>SO\(_4^{2-}\)>Cl\(^-\).
Step 4: Conclusion.
Thus, the higher the valency of the oppositely charged ion, the greater its coagulating power.