JEE Main · 2023 · 25 Jan 2023 · Shift 2 · Surface Chemistry

Anhydrous calcium chloride takes water vapour into its bulk to form hydrates, which is absorption rather than adsorption, so the first statement is incorrect. Adsorption lowers the residual surface forces and hence the surface energy, so that statement is correct. As the surface fills, the most active sites are occupied first and the enthalpy of adsorption grows less negative as the process continues, not more negative, so that statement is incorrect. Because freely moving molecules become confined on the surface, the entropy of the system falls during adsorption, so that statement is correct. The number of incorrect statements is two.