Glossary — Key Terms in Solutions & Colligative Properties — Notes

Term	Definition
Solution	Homogeneous mixture of two or more components; solvent = major component, solute = minor component
Molality (m)	Moles of solute per kilogram of solvent (mol/kg); temperature-independent
Molarity (C or M)	Moles of solute per litre of solution (mol/L); temperature-dependent
Mole fraction (x)	Ratio of moles of one component to total moles of all components
Raoult's Law	Partial vapour pressure of each component equals its mole fraction × pure component vapour pressure
Henry's Law	Partial pressure of dissolved gas = Henry's constant × mole fraction of gas in solution
Colligative property	Property that depends only on the number of solute particles, not their identity
Van't Hoff factor (i)	Ratio of observed colligative property to theoretical (non-electrolyte) value; accounts for dissociation/association
Degree of dissociation (α)	Fraction of solute molecules that dissociate into ions (0 ≤ α ≤ 1)
Degree of association (α)	Fraction of solute molecules that aggregate into clusters (0 ≤ α ≤ 1)
Ideal solution	Solution obeying Raoult's law at all compositions; $\Delta H$ _mix = 0, $\Delta V$ _mix = 0
Azeotrope	Mixture that boils at constant temperature and composition; cannot be separated by distillation
Minimum boiling azeotrope	Formed by positive deviation solutions; boils at lower T than either pure component
Maximum boiling azeotrope	Formed by negative deviation solutions; boils at higher T than either pure component
Osmosis	Spontaneous flow of solvent through a semipermeable membrane from dilute to concentrated solution
Osmotic pressure (π)	Minimum pressure required to stop osmosis; π = iCRT
Reverse osmosis	Solvent flow from concentrated to dilute under applied external pressure > π
Isotonic solutions	Solutions with equal osmotic pressures; no net osmotic flow between them
Hypertonic	Solution with higher osmotic pressure than the reference (e.g., blood)
Hypotonic	Solution with lower osmotic pressure than the reference
Ebullioscopic constant (Kb)	Molal boiling point elevation constant; Kb(water) = 0.52 K·kg/mol
Cryoscopic constant (Kf)	Molal freezing point depression constant; Kf(water) = 1.86 K·kg/mol
Henry's Law constant (K_H)	Constant of proportionality in p = K_H × x; increases with temperature
Semipermeable membrane	Membrane that selectively allows solvent molecules to pass but not solute
Haemolysis	Bursting of red blood cells placed in hypotonic solution due to osmotic water influx
Crenation	Shrinkage of red blood cells placed in hypertonic solution due to osmotic water loss