Chapter 13: Properties of Solutions

The molecular basis of dissolution is explored through the lens of intermolecular forces, with particular emphasis on how solvation and hydration processes involve the transfer of energy between solute and solvent particles. Understanding solubility requires consideration of multiple variables including temperature, pressure, and the polar or nonpolar character of both the dissolved substance and the dissolving medium, with Henry's law providing quantitative predictions for gas solubility in liquids. The chapter presents a comprehensive treatment of concentration units, establishing that molarity, molality, mass percent, mole fraction, and parts per million or billion each serve specific purposes depending on the application and context. Colligative properties form a central theme, demonstrating that vapor-pressure lowering, boiling-point elevation, freezing-point depression, and osmotic pressure depend solely on the number of solute particles rather than their chemical identity, with Raoult's law enabling calculations of vapor-pressure changes in solutions. The van't Hoff factor extends this framework to ionic solutions by accounting for dissociation behavior of electrolytes. The chapter acknowledges deviations from ideal solution behavior and explores practical applications ranging from antifreeze formulations to food preservation methods and the maintenance of osmotic balance in biological systems. Finally, colloids are presented as a distinct category of mixtures with unique properties arising from their colloidal particle size, including discussion of preparation methods and stabilization mechanisms that prevent particle aggregation. Throughout, students develop both qualitative and quantitative reasoning about how dissolved substances modify the physical properties of solutions.