The following statements relate to the adsorption of gases on a solid surface. Identify the incorrect statement among them:

Let us understand the process of adsorption. Adsorption occurs when gas molecules (adsorbate) adhere to the surface of a solid (adsorbent) due to unbalanced forces on the solid surface. We need to evaluate each statement to identify which one is incorrect.

Starting with option A: "Entropy of adsorption is negative." Entropy measures disorder. During adsorption, gas molecules lose freedom as they move from a random gaseous state to a confined state on the surface. This reduces disorder, so the entropy change ($$\Delta S$$) is negative. Hence, this statement is correct.

Option B: "Enthalpy of adsorption is negative." Adsorption is typically exothermic because energy is released when bonds form between the adsorbate and adsorbent. Thus, the enthalpy change ($$\Delta H$$) is negative. This holds for physical adsorption and most chemisorption. Therefore, this statement is correct.

Option C: "On adsorption decrease in surface energy appears as heat." Adsorption reduces the surface energy of the solid because the adsorbate molecules lower the surface tension. The energy released due to this decrease manifests as heat, aligning with the exothermic nature of adsorption. Thus, this statement is correct.

Option D: "On adsorption, the residual forces on the surface are increased." Residual forces are the unbalanced forces on the solid surface that drive adsorption. When adsorption occurs, these forces are satisfied as adsorbate molecules bind to active sites, reducing the surface's residual forces. Therefore, the residual forces decrease, not increase. This makes the statement incorrect.

Hence, the correct answer is Option D.