Q1: The change in enthalpy, when a unit quantity of gas is absorbed by relatively large quantity of adsorbent (on which a definite concentration of the adsorbed gas already exists) is termed as the

ANS:A - differential heat of adsorption.

The change in enthalpy when a unit quantity of gas is absorbed by a relatively large quantity of adsorbent, where a definite concentration of the adsorbed gas already exists, is termed as the integral heat of adsorption. Integral heat of adsorption refers to the total heat absorbed or released during the adsorption process, taking into account the change in enthalpy of both the adsorbate (gas) and the adsorbent. It considers the enthalpy change from the initial state, where no gas is adsorbed, to the final state, where the desired amount of gas is adsorbed onto the adsorbent. The differential heat of adsorption, on the other hand, refers to the change in enthalpy when an additional small amount of gas is adsorbed onto the surface of the adsorbent. It represents the enthalpy change associated with adsorbing an incremental amount of gas onto the surface. Heat of wetting is a term used in the context of liquids, referring to the enthalpy change when a solid surface is wetted by a liquid. It is not directly related to the absorption of gases by adsorbents. Therefore, the correct term for the described scenario is the integral heat of adsorption.