Question:

Methylene blue is adsorbed on activated charcoal at 250°C from its aqueous solution. Which is the correct statement for this process?

The adsorption is irreversible.

The adsorption requires activation at 250°C.

The adsorption is accompanied by a decrease in enthalpy.

The adsorption increases with increase of temperature.

Adsorption of methylene blue on activated charcoal is physical adsorption. Hence, it is characterised by decrease in enthalpy.