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🧪 Chemistry  ·  Surface Chemistry  ·  NEET & JEE

Which observation supports the idea that chemisorption, unlike physisorption, requires activation energy?

Answer: Chemisorption rate often increases with temperature up to an optimum, similar to chemical reactions.

  • A Chemisorption decreasing steadily with temperature right from the very start as widely reported
  • B Chemisorption rate often increases with temperature up to an optimum, similar to chemical reactions
  • C Chemisorption showing no dependence whatsoever on the surrounding temperature in standard practice
  • D Chemisorption usually proceeding instantly regardless of the temperature applied under most conditions encountered

Correct answer: B. Chemisorption rate often increases with temperature up to an optimum, similar to chemical reactions

Explanation: Because chemisorption involves bond formation with an activation energy barrier, its rate often increases with temperature up to an optimum, unlike physisorption.

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.

Read the full Surface Chemistry notes →