Dissolution energetics:\nOn which factors does the heat of solution depend most strongly?

Introduction / Context:
The heat of solution (enthalpy of solution) quantifies thermal effects when a solute dissolves in a solvent. It is a central concept for designing dissolution, crystallization, and extraction processes, as it affects temperature control, energy balances, and safety (hot or cold packs are practical examples).

Given Data / Assumptions:

• Dissolution occurs without chemical reaction beyond solvation/ionization.
• Usual concentration ranges where non-ideal effects may be significant.
• Ambient pressure variations have negligible enthalpy effect.

Concept / Approach:
The heat of solution reflects competing energy changes: breaking solute–solute and solvent–solvent interactions (endothermic) versus forming solute–solvent interactions (exothermic). The balance depends on both the nature of the solute (ionic vs molecular, lattice enthalpy) and the solvent (polarity, hydrogen bonding). Concentration matters because local structure and activity coefficients change with composition, altering incremental heats of dilution and solution.

Step-by-Step Discussion:

Verification / Alternative check:
Tabulated differential heats of solution show composition dependence; comparing NaCl in water vs ethanol demonstrates solvent effects; comparing NaCl vs KNO3 in water demonstrates solute effects.

Why Other Options Are Wrong:

• Each single-factor option is incomplete; all listed factors contribute significantly.

Common Pitfalls:
Assuming heats of solution are constant; ignoring strong composition dependence; overlooking solvent structural effects.

Final Answer:
All of (a), (b), and (c).