Question

Assertion (A): Addition of an excess electrolyte to the colloidal solution leads to the precipitation of colloidal particles.
Reason (R): The charged electrolyte particles neutralises the oppositely charged colloidal particles and promotes coagulation of colloidal sols.

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A)
• B. Both (A) and (R) are correct but (R) is not the correct explanation of (A)
• C. (A) is correct but (R) is incorrect
• D. (A) is incorrect but (R) is correct

Hint:

Electrolytes destabilize colloids by neutralizing surface charge → causes coagulation.

Answer 1

The Correct Option is A

Step 1: Basis of colloidal stability.
Colloidal particles repel each other due to similar surface charges, preventing aggregation.

Step 2: Effect of added electrolyte.
Excess electrolyte supplies counterions that neutralize the particle charges, diminishing electrostatic repulsion.

Step 3: Coagulation outcome.
Charge neutralization causes particles to lose stability, aggregate, and precipitate.

Step 4: Evaluating Assertion and Reason.
Both statements are true; the reason accurately explains why electrolyte addition induces precipitation via charge neutralization.

Step 5: Conclusion.
Both A and R are correct, and R is the correct explanation of A.