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: Understanding colloidal stability.
Colloidal particles remain stable due to the presence of like charges on their surface, which prevents aggregation due to electrostatic repulsion.

Step 2: Effect of electrolyte addition.
When excess electrolyte is added, oppositely charged ions are attracted to colloidal particles and neutralize their charge. This reduces repulsion between particles.

Step 3: Coagulation process.
Once the charge is neutralized, colloidal particles lose stability and aggregate together, leading to precipitation or coagulation.

Step 4: Evaluating assertion and reason.
Both statements are correct: addition of electrolyte causes precipitation, and the reason correctly explains charge neutralization leading to coagulation.

Step 5: Final conclusion.
Thus, both A and R are correct, and R is the correct explanation of A.
Final Answer: \[ \boxed{\text{Both A and R are correct and R is the correct explanation of A}} \]