Which one of the following is correct for the adsorption of a gas at a given temperature on a solid — Surface Chemistry Chemistry Question

💡 Solution & Explanation

During adsorption, there is always a decrease in residual forces of the surface, i.e., there is decrease in surface energy which appears as heat. Adsorption, therefore, is invariably an exothermic process. In other words, ∆H of adsorption is always negative. When a gas is adsorbed, the freedom of movement of its molecules become restricted. This amounts to decrease in the entropy of the gas after adsorption, i.e., ∆S is negative. Adsorption is thus accompanied by decrease in enthalpy as well as decrease in entropy of the system.