In this worksheet, we will practice describing the solvation mechanisms of molecules and ionic solids and the enthalpic and entropic changes involved.
Why are and ions strongly solvated in water but not in hexane?
- AHexane molecules are much larger than water molecules, so they cannot pack around the small sodium and chloride ions as easily as water can.
- BChloride ions deprotonate water molecules, and the resulting ion-ion interactions are stronger in total than the ionic bonds of sodium chloride. Hexane cannot be deprotonated and thus interacts with ions far more weakly.
- CIon-dipole forces between the ions and water are stronger that the hexane-ion forces because hexane is nonpolar and thus interacts with ions far more weakly.
- DDissolution of ions in hexane is entropically costly, as interactions with ions force the hexane molecules into less flexible folded conformations.
- EWater molecules are bent, so ions can occupy the space between bonds. Hexane molecules are straight and thus cannot interact with ions in this way.