Why does physisorption decrease with the increase of temperature?

Answer

Physiosorption exothermic process that means heat is evolved in this process. Le chatelier’s principle is used in predicting the effect of change in temperature or pressure on chemical equilibrium.

 According to this principle, if some change is made in the state of the system, the system will change itself accordingly so that the effect of change of state is negligible.

 In case of physical adsorption, heat is evolved. This means the temperature of the surrounding will increase and we are also increasing temperature. So, according to le chatelier’s principle, the system will move in that direction in which temperature will decrease. Therefore the reaction will move towards backward direction in order to decrease the temperature (as the reaction is exothermic in forward direction). So, the rate of physisorption decreases with increase in temperature.