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JEE Advanced · Chemistry · 19. Surface Chemistry

Methylene blue, from its aqueous solution, is adsorbed on activated charcoal at 25o C. For this process, the correct statement is 

  1. A The adsorption requires activation at 25oC.
  2. B The adsorption is accompanied by a decrease in enthalpy
  3. C The adsorption increases with increase of temperature.
  4. D The adsorption is irreversible.
Verified Solution

Answer & Solution

Correct Answer

(B) The adsorption is accompanied by a decrease in enthalpy

Step-by-step Solution

Detailed explanation

It is the process of Physical adsorption as charcoal is already activated.
Since physical adsorption is spontaneous  Δ G  is -ve
Δ G = Δ H - T Δ S
as Δ S  is -ve (passage of methylene blue from aqueous phase over the surface of adsorbent) i.e. Δ H  is highly -ve since process is exothermic in nature. Physical adsorption is reversible in nature.
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