Question

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

• A. The adsorption requires activation at ${25}^{o}C$
• B. The adsorption is accompanied by a decrease in enthalpy
• C. The adsorption increases with increase of temperature
• D. The adsorption is irreversible

Answer 1

The correct option is B The adsorption is accompanied by a decrease in enthalpy

Methylene blue is adsorbed on activated charcoal at ${25}^{o}C$ from its aqueous solution. For this process, the adsorption is accompanied by a decrease in enthalpy. Adsorption is physisorption and hence, the energy of activation is not required.

Physisorption is exothermic and reversible and it decreases with an increase in temperature. The process, which does not involve any surface reaction, is achieved quickly at low temperatures.