What is Solubility? • Describes the amount of solute that dissolves in a solvent.
Driving Forces of Solubility Enthalpy: • Total energy of a chemical system • The enthalpy change (∆H) is the amount of heat released or absorbed when a chemical reaction occurs at constant pressure.
Driving Forces of Solubility Entropy: • Randomness • Things like to become more random.
Entropy *Entropy increases as a substance changes from solid to liquid to gas
When a solid dissolves, attractive forces are weakened, and randomness increases. *If exothermic (gives off heat), dissolving takes place. *Endothermic (absorbs heat) can occur if randomness term is greater. Youtube Video - Dissolving in Endothermic Reaction As ice melts, entropy increases
Temperature and Solubility About 95% of solids are most soluble at high temperatures. Solids = direct relationship for temperature and solubility
Temperature and Solubility Gases have no crystal lattice energy. Dissolving of a gas is generally exothermic, and favored at lower temperatures. Gases = indirect relationship for temperature and solubility
Pressure and Solubility Pressure only affects the solubility of gases. As air pressure increases, solubility of a gas increases. Direct Relationship Pressure and Carbonation Video
Nature and Solubility Whether polar or nonpolar. *Like dissolves like The rule of thumb is that "like dissolves like". Polar/ionic solvents dissolve polar/ionic solutes and non-polar solvents dissolve non-polar solutes. Water Dissolving Salt Video Oil Dissolution Video Oil In Water Video