Henry's Law: p = K_H × x. K_H increases with temperature → gas solubility decreases with increasing temperature. Application: carbonated drinks, "the bends" in divers.

Raoult's Law: P_A = x_A·P°_A for each component. Total pressure = x_A·P°_A + x_B·P°_B (ideal, volatile binary). For non-volatile solute: $\Delta P$/P° = x_solute.

Ideal solutions: $\Delta H$_mix = 0, $\Delta V$_mix = 0, obeys Raoult's law. $\Delta S$_mix > 0 (always). Examples: benzene + toluene, n-hexane + n-heptane.

Positive deviation: A-B interactions weaker → P_obs > P_Raoult → $\Delta H$_mix > 0, $\Delta V$_mix > 0 → minimum boiling azeotrope. Example: ethanol + water.

Negative deviation: A-B interactions stronger → P_obs < P_Raoult → $\Delta H$_mix < 0, $\Delta V$_mix < 0 → maximum boiling azeotrope. Example: $CHCl_{3}$ + acetone.

Four colligative properties (all depend on number of particles, not nature):

1. Relative lowering of VP: $\Delta P$/P° = x_solute
2. Boiling point elevation: $\Delta Tb$ = iKbm (Kb water = 0.52 K·kg/mol)
3. Freezing point depression: $\Delta Tf$ = iKfm (Kf water = 1.86 K·kg/mol)
4. Osmotic pressure: π = iCRT

Water constants: Kb = 0.52, Kf = 1.86 (Kf > Kb because $\Delta Hf$us < $\Delta Hv$ap). Camphor Kf = 40 K·kg/mol (largest — used in Rast's method).

Molar mass determination: $M_{2}$ = Kb × w_{2} × 1000 / ($\Delta Tb$ × w_{1}). Osmotic pressure most sensitive for macromolecules.

Van't Hoff factor (i): i = observed / theoretical. Dissociation: i > 1; i = 1 + (n−1)α. Association: i < 1; i = 1 − α/2 (for dimers). NaCl: i=2; $K_{2}SO_{4}$: i=3; $AlCl_{3}$: i=4; $CH_{3}COOH$ in benzene: i=0.5.

Association effect on molar mass: i < 1 → fewer particles → smaller colligative effect → apparent M > true M. Dissociation → apparent M < true M.

Osmosis: Solvent flows from lower to higher osmotic pressure through a semipermeable membrane. Reverse osmosis: apply P_ext > π to purify water.

Isotonic, hypertonic, hypotonic: Cells in hypotonic solution swell (haemolysis); in hypertonic they shrink (crenation); isotonic = no net flow (0.9% NaCl for blood).