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🧪 Chemistry  ·  Surface Chemistry  ·  NEET & JEE

A given mass of activated charcoal adsorbs a gas according to the Freundlich isotherm with n = 2. If the pressure of the gas is quadrupled, by what factor does x/m increase, all else being constant?

Answer: 2 times.

  • A 2 times
  • B 4 times
  • C 8 times
  • D 16 times

Correct answer: A. 2 times

Explanation: x/m = k.P<sup>1/n</sup> = k.P<sup>1/2</sup>. If P becomes 4P, x/m becomes k(4P)<sup>0.5</sup> = k.P<sup>0.5</sup> x 2, so x/m increases by a factor of 2.

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 →