Q1: As complete saturation of an adsorbent is approached, the differential heat of adsrop-tion approaches

ANS:A - that of normal condensation.

In the context of "that of normal condensation," it refers to the enthalpy change associated with the phase transition of a substance from its gaseous phase to its liquid phase at its saturation point, which is commonly known as condensation. During condensation, molecules in the vapor phase lose energy as they transition to the liquid phase. This energy loss is reflected as a decrease in enthalpy, which is the measure of the total energy of a system under constant pressure. The enthalpy change associated with condensation is typically referred to as the heat of condensation. When a substance condenses at its saturation point, it undergoes a phase transition where its vapor phase becomes saturated with vapor molecules, meaning that it contains the maximum amount of vapor that can be present at a given temperature and pressure. At this point, further condensation would not occur without a change in temperature or pressure. The enthalpy change associated with condensation at the saturation point is often referred to as the "normal" enthalpy of condensation. It represents the energy released per unit mass or per mole of the substance as it transitions from the vapor phase to the liquid phase at the saturation conditions. Therefore, when it is mentioned that "the differential heat of adsorption approaches that of normal condensation," it means that as the adsorbent becomes saturated, the energy change associated with adsorption approaches the energy change observed during the condensation of the adsorbate from its gaseous phase to its liquid phase at saturation conditions. In both cases, the energy change becomes increasingly negligible as saturation is approached.