Chapter 13- Solutions and Colligative Properties Colligative Properties

Colligative Properties - depend on the concentration of the solution, not on the type of particle dissolved. Vapor Pressure of Solutions: Vapor pressure decreases as concentration increases. Raoult's Law: P soln = X solvent P solvent ideal solutions obey Raoult's Law Animation

Boiling Point Elevation: boiling point increases as concentration increases. ΔT b = K b m molal boiling point constant Table 13.4 p. 549 Freezing Point Depression: freezing point decreases as concentration increases. ΔT f = K f m molal freezing point constant Table 13.4 p.549

Osmosis: net movement of solvent toward the more concentrated solution through a semipermeable membrane. The minimum pressure that stops osmosis is the osmotic pressure. π = MRT

Electrolyte Solutions For a 1 molal water solution we would expect T f to be C but for NaCl it is twice that because NaCl dissociates into Na + and Cl - which is twice as many particles. van't Hoff Factor, i = moles of particles in solution moles of solute dissolved Usually colligative effects for an electrolyte are a little less than predicted due to solute-solute and solute-solvent interactions. ΔT = i K m П = i MRT

Colloids - suspension of tiny particles in a medium. Cloudiness of mixture can be observed by eye or by passing light through the mixture (Tyndall Effect)

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