u Because dissolved particles affect vapor pressure - they affect phase changes. u Colligative properties depend only on the number - not the kind of solute particles present  Useful for determining molar mass

u Because a non-volatile solute lowers the vapor pressure it raises the boiling point. u The equation is:  T = K b m solute u  T is the change in the boiling point u K b is a constant determined by the solvent. u m solute is the molality of the solute

u Because a non-volatile solute lowers the vapor pressure of the solution it lowers the freezing point. u The equation is:  T = K f m solute u  T is the change in the freezing point u K f is a constant determined by the solvent  m solute is the molality of the solute

1 atm

u Colligative properties only depend on the number of solute particles. u Ionic compounds should have a bigger effect. u When they dissolve they dissociate. u Individual Na and Cl ions separate. u 1 mole of NaCl makes 2 moles of ions. u 1mole Al(NO 3 ) 3 makes 4 moles ions

Applications of Colligative Properties: Dialysis: The process where solvent and other small molecules pass through a membrane. Similar to osmosis but the “holes” in the membrane are larger which allows hydrated ions to pass through. In hemodialysis an isotonic solution is used to prevent loss of important electrolytes and glucose. Solution composition: 0.6% NaCl, 0.04% KCl, 0.2% NaHCO 3, 0.72% glucose

Colloids Homogeneous mixtures of two or more substances which are not solutions. Particles are larger than those found in solutions, but are still too small to settle out of solution by gravity. Dispersed phase: Solute-like Continuous phase: Solvent-like

Unlike solutions, colloids exhibit light scattering called the Tyndall effect.

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