Question

The ability of anion to bring about coagulation of a given colloid depends upon

• A. its charge
• B. the sign of the charge alone
• C. the magnitude of its charge
• D. both magnitude and sign of its charge

Answer 1

The Correct Option is D

To understand the ability of an anion to bring about coagulation of a given colloid, we need to consider some fundamental concepts regarding colloids and coagulation.

Concept of Coagulation:

Coagulation or flocculation refers to the process where colloidal particles come together to form larger aggregates or precipitate out of the dispersion medium. This happens when the stability of the colloid is disrupted.

Factors Affecting Coagulation:

1. Charge on Colloids: Colloidal particles typically carry an electric charge. The nature and magnitude of this charge can influence stability and coagulation.
2. Counter Ions: When ions of opposite charge (counter ions) are added, they neutralize the charge on the colloidal particles. This neutralization encourages particles to aggregate and settle out.

Application of Electrolytes:

The valency and charge of the counter ions (in this case, anions) are crucial in destabilizing the colloid:

1. Magnitude of Charge: The coagulative power of an ion is directly proportional to the magnitude of its charge, i.e., higher valency ions have more coagulating power.
2. Sign of Charge: The ability to neutralize the charge depends on having an opposite sign of charge.

This leads us to the conclusion that the ability of an anion to bring about coagulation of a given colloid depends upon both the magnitude and sign of its charge.

Conclusion:

The correct answer to the question is both magnitude and sign of its charge because anions with higher charges are more effective at coagulating colloids and must have the opposite charge to neutralize colloidal particles.