Question

Assertion A: At high electrolyte concentration, dispersed systems becomes coagulated. Reason R: Repulsive forces among particles are greatly reduced.

• 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 not correct
• D. A is not correct but R is correct

Hint:

Electrolytes "screen" the charge. Less charge = Less repulsion = Coagulation.

Answer 1

The Correct Option is A

Step 1: Concept
The stability of colloidal and dispersed systems is often explained by the DLVO theory, which considers the balance between attractive and repulsive forces.

Step 2: Meaning
Coagulation is the process where particles come together to form large aggregates.

Step 3: Analysis
Adding electrolytes increases the ionic strength, which compresses the electrical double layer around the particles. This reduces the zeta potential and the electrostatic repulsive forces. When repulsion is lower than the van der Waals attractive forces, the particles collide and stick together (coagulate).

Step 4: Conclusion
Both statements are correct, and the reduction in repulsive forces is the direct cause of coagulation at high electrolyte concentrations.

Final Answer: (A)