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A negatively charged colloidal sol is coagulated by adding electrolytes containing Na+, Ba<sup>2+</sup>, and Al<sup>3+</sup> ions separately. According to the Hardy-Schulze rule, which ion will coagulate the sol most effectively?

Answer: Al 3+.

  • A Na+
  • B Ba<sup>2+</sup>
  • C Al<sup>3+</sup>
  • D All will coagulate equally

Correct answer: C. Al<sup>3+</sup>

Explanation: The Hardy-Schulze rule states that ions with higher valency are more effective coagulants for oppositely charged sols, so Al<sup>3+</sup> (3+) is most effective.

Adsorption Isotherm: x/m vs PressureP (pressure)x/mlow P: x/m ∝ Phigh P: saturation plateauAt high pressure, all surface sites are occupied - the curve flattens (monolayer saturation)

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.

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