Discussion Forum



1)

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 $25^{0}$ C

B) the adsorption is accompanied by a decreases in enthalpy

C) the adsorption increses with increases of temperature

D) the adsorption is irreversible

Answer:

Option B

Explanation:

Plan  Physical  adsorption takes place with a decrease in enthalpy thus exothermic change

It is physical adsorption and does not require activation. Thus, (a) is incorrect.

Being  physical adsorption  $\triangle$ H <0  thus, (b) is correct. An exothermic reaction is favoured at low temperature thus (c) is incorrect.

 Physical adsorption is always reversible, thus (d) is incorrect.