Question

In general, the attractive intermolecular forces between solvent and solute particles must be comparable or greater than solute-solute interactions for significant solubility to occur. Explain this statement in terms of the overall energetics of solution formation.

Short answer

In summary, solubility is significantly influenced by the attractive intermolecular forces between solvent and solute particles, which must be comparable or greater than solute-solute interactions to achieve favorable energetics of solution formation. This ensures that the energy released from solvent-solute interactions sufficiently compensates for the energy needed to overcome solute-solute and solvent-solvent interactions, resulting in a more favorable overall energy change (ΔHsoln) and, consequently, increased solubility.

Step-by-step solution

Understand the components of solution formation energetics

The overall energy associated with solution formation can be divided into three main parts: 1. Energy required to overcome solute-solute interactions (ΔH1) 2. Energy required to overcome solvent-solvent interactions (ΔH2) 3. Energy released when solvent-solute interactions are formed (ΔH3) The sum of these energy changes results in the overall energy change of the process, ΔHsoln.

Relate the energy changes to solubility

For a solution to form, the overall energy change (ΔHsoln) must be favorable, which means it should not be highly positive or endothermic. This means that the energy released when solvent-solute interactions form (ΔH3) must compensate for the energy required to overcome solute-solute (ΔH1) and solvent-solvent interactions (ΔH2).

Explain why comparable solvent-solute interactions are necessary

If the attractive intermolecular forces between solvent and solute are much weaker than the solute-solute and solvent-solvent interactions, the energy released upon forming solvent-solute interactions (ΔH3) would not be sufficient to overcome the energy required to break the solute-solute and solvent-solvent interactions (ΔH1 and ΔH2). In this case, the overall energy change (ΔHsoln) would be highly positive, making the solution formation energetically unfavorable. On the other hand, if the attractive intermolecular forces between solvent and solute are comparable to or greater than those between the solute-solute and solvent-solvent interactions, the energy released upon forming solvent-solute interactions (ΔH3) would be enough to compensate for the energy required to overcome the solute-solute and solvent-solvent interactions (ΔH1 and ΔH2). Therefore, the overall energy change (ΔHsoln) would be more favorable, and the solute is more likely to dissolve in the solvent.

Conclude the explanation

In conclusion, for significant solubility to occur, the attractive intermolecular forces between solvent and solute particles must be comparable or greater than solute-solute interactions. This is because the overall energetics of solution formation must be favorable, allowing the energy released from solvent-solute interactions to compensate for the energy required to overcome solute-solute and solvent-solvent interactions.