Chemical engineering thermodynamics concept check:\nWhat is the enthalpy change called when one unit mass of a dry solid is wetted with enough liquid such that additional liquid causes no further thermal effect?

Introduction / Context:
When a porous or particulate solid contacts a liquid, heat is released or absorbed due to surface interactions and spreading of the liquid on the solid. Chemical engineers distinguish between the initial heat liberated upon first contact and the limiting amount after the solid is fully and uniformly covered. Correct terminology matters in drying, granulation, crystallization, and adsorption design.

Given Data / Assumptions:

• Dry solid is contacted with a wetting liquid at constant initial temperature and pressure.
• Enough liquid is added to completely cover/penetrate accessible surface so that additional liquid no longer changes temperature.
• No chemical reaction between solid and liquid; effect is purely physical wetting.

Concept / Approach:
Two related quantities are used. The heat of wetting refers to the enthalpy change when the first portions of liquid spread on a unit mass of dry solid. The heat of complete wetting is the total enthalpy change when sufficient liquid has been added to fully wet the solid so that further addition produces no incremental thermal effect. The question clearly describes the limiting case, hence the latter term applies.

Step-by-Step Solution:
Interpret the stem: “sufficient liquid” and “no additional thermal effect” indicate a limiting, not incremental, condition.Map terminology: limiting condition → “complete wetting.”Therefore, select the term “heat of complete wetting.”

Verification / Alternative check:
In calorimetry, the integral heat effect measured up to the point of saturation (complete surface coverage) is reported as heat of complete wetting; the differential slope at low additions corresponds to heat of wetting.

Why Other Options Are Wrong:
Heat of mixing relates to miscible liquids/solutions; heat of adsorption concerns gas or solute binding on solid surfaces; “heat of wetting” is incremental and not necessarily the terminal value; heat of dilution involves adding solvent to a solution, not to a dry solid.

Common Pitfalls:
Confusing incremental versus integral definitions and overlooking the phrase indicating “no further effect.”

Final Answer:
heat of complete wetting