Question

The correct statement(s) related to colloids is (are):

Preparation of colloidal sol of metals like gold and platinum using electrical disintegration involves both dispersion and condensation.

When FeCl$_3$ is added to excess of hot water, a negatively charged sol of hydrated ferric oxide is formed due to the adsorption of hydroxide ions.

Lyophilic colloids have a unique property of protecting lyophobic colloids.

For hydrogenation reaction, the catalytic activity increases from group 5 to group 11 metals with maximum activity being shown by group 7-9 elements of the periodic table.

• A. Preparation of colloidal sol of metals like gold and platinum using electrical disintegration involves both dispersion and condensation.
• B. When FeCl$_3$ is added to excess of hot water, a negatively charged sol of hydrated ferric oxide is formed due to the adsorption of hydroxide ions.
• C. Lyophilic colloids have a unique property of protecting lyophobic colloids.
• D. For hydrogenation reaction, the catalytic activity increases from group 5 to group 11 metals with maximum activity being shown by group 7-9 elements of the periodic table.

Answer 1

Answer: (A), (B), (C)

Statements (i), (ii), and (iii) are correct.

Answer 2

1. Electrical Disintegration: In this method, bulk metals are broken into fine particles (dispersion) which then coalesce into colloidal particles (condensation). Hence, the statement is correct.

2. Hydrolysis of FeCl₃: When FeCl₃ is added to excess hot water, hydrolysis occurs, forming a sol of hydrated ferric oxide. The adsorption of hydroxide ions on the surface imparts a negative charge to the colloidal particles. This statement is correct.

3. Lyophilic Protective Action: Lyophilic colloids adsorb onto the surface of lyophobic colloids, thereby “protecting” them from coagulation. This statement is correct.

4. Catalytic Activity in Hydrogenation: The trend in catalytic activity for hydrogenation does not simply increase from group 5 to group 11. In fact, maximum catalytic activity is observed for metals in groups 7–9, and the activity decreases beyond that. Hence, the statement as given is misleading/incorrect.