JEE Advanced · 2013 · 02 Jun 2013 · Paper 1 · Surface Chemistry

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

(A)The adsorption requires activation at 25 °C.
(B)The adsorption is accompanied by a decrease in enthalpy.✓ Correct
(C)The adsorption increases with increase of temperature.
(D)The adsorption is irreversible.

Answer: (B)

Solution

This is a process of physical adsorption (physisorption). Physical adsorption is exothermic, meaning it releases energy and is accompanied by a decrease in enthalpy (

Δ H < 0

). It does not require activation energy, decreases with increasing temperature (being exothermic), and is reversible.

JEE Advanced · 2013 · 02 Jun 2013 · Paper 1 · Single correct option

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