Final answer:
The dissolution of salts involves overcoming solute-solute and solvent-solvent interactions (endothermic processes) and forming solute-solvent interactions (exothermic process). The overall enthalpy change, which can be either endothermic or exothermic, dictates the ease of dissolution and is determined by the relative strengths of these interactions.
Step-by-step explanation:
Enthalpy Changes in Salt Dissolution
Dissolution of salts in water is a fundamental chemical process characterized by specific enthalpy changes. The physical description of this process involves understanding the types of enthalpies contributing to salt dissolution. There are three main interactions to consider: solute-solute, solvent-solvent, and solute-solvent forces.
Initially, to dissolve a salt, energy is absorbed to overcome the solute-solute interactions, which is an endothermic process. Concurrently, energy is required to disrupt the solvent-solvent interactions, particularly in water where hydrogen bonds must be broken. When the salt begins to dissolve, ions are surrounded by water molecules in a process known as hydration or solvation, which is exothermic as energy is released due to the formation of solute-solvent attractions.
The overall energy change of the dissolution can be either endothermic or exothermic, depending on which of these steps absorbs or releases more energy. When the solute-solvent interactions are stronger than the solute-solute and solvent-solvent interactions, dissolution generally occurs more readily, often releasing energy. In contrast, if the solute-solute interactions are much stronger, as is the case with calcium carbonate, dissolution might require additional energy and occur to a lesser extent.
The enthalpy change of dissolution is therefore vital in determining whether a salt will dissolve in water and to what extent. This process also relates to the concept of Gibbs free energy change as the driving force for dissolution. Salts like sodium chloride (table salt) are examples where dissolution is typically exothermic due to strong solute-solvent interactions surpassing the solute-solute and solvent-solvent attractions.
Understanding these enthalpic considerations is crucial for predicting the behavior of a salt in aqueous solution and is applicable to the wider context of solubility equilibria, encompassing phenomena such as the common ion effect and supersaturation.