AP Chemistry / Unit 9: Thermodynamics and Electrochemistry
9.6 Free Energy of Dissolution
Notes
Dissolving involves breaking solute-solute and solvent-solvent attractions (endothermic) and forming solute-solvent attractions (exothermic). Entropy usually increases. Both decide whether dissolving is favorable.
Practice
Ammonium nitrate dissolves even though it's endothermic because:
$-T\Delta S$ wins.
Forming solute-solvent attractions:
Attractions forming are exothermic.
Dissolving a solid in water usually makes $\Delta S$:
Particles spread out.
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