Answer: NaCl less than MgCl2 less than AlCl3.
- A AlCl3 less than MgCl2 less than NaCl
- B NaCl less than MgCl2 less than AlCl3
- C MgCl2 less than NaCl less than AlCl3
- D All three are equally effective regardless of cation charge
Correct answer: B. NaCl less than MgCl2 less than AlCl3
Explanation: Coagulating power increases with the valency of the oppositely charged ion. Since the sol is negative, cations matter: Na+ (1+) is weakest, Mg2+ (2+) is intermediate, and Al3+ (3+) is the strongest coagulant.
A typical adsorption isotherm: x/m (mass adsorbed per gram of adsorbent) rises steeply at low pressure, then flattens into a saturation plateau as the adsorbent surface fills up.
Concept context
Explore the chemistry that happens at interfaces, from catalysts that speed up industrial reactions to colloids like milk, smoke, and gels that surround us every day.