contemplated with

Combined with Explains almost all Solution behaviors We saw three examples of Colligative Properties: colligative – depends only on the number of particles  T fp = K fp m solute  T bp = K bp m solute  P solv = X solvent P o solvent  T fp = K fp m solute  T bp = K bp m solute  P solv = X solvent P o solvent See why we need to deal with new types of concentration: mole fraction, molality. These relationships depend on numbers of particles

Ideal behavior, no association of ions Ideal behavior, no association of ions Let’s watch this association ….

Combined with Explains almost all Solution behaviors Fourth example of Colligative Properties: Osmosis – the movement of solvent through a semi- permeable membrane from a region of high solute concentration to low solute concentration.

pasta marshmallow nut light source Semi- Permeable Membrane bag 5% sugar solution This is the system at equilibrium This is what creates the dis-equilibrium In the beaker

pasta marshmallow nut light source The system is disturbed away from equilibrium X H 2 O (outside) ≠ X H 2 O (inside) 100% H 2 O (outside) ≠ 95% H 2 O (inside) The system will respond by shifting equilibrium H 2 O (outside)  H 2 O (inside) How???

Only water molecules can move thorough membrane The membrane is invisible to water

pasta marshmallow nut light source When the system responds by shifting equilibrium: If diluted to 1% sugar: mol/ L = M Using:  = c R T  = M x atm/M K x 298 K  = atm or 544 mm Hg The sugar solution under pressure rises up the tube, like a manometer. The height represents the Osmotic Pressure

light source Water fills beaker corn syrup pipet fits tightly into hole core of carrot removed and filled with corn syrup Carrot As a membrane

pasta marshmallow nut light source

 = c R T  in: atm mol/L kelvin .0820 L/atm K Combined with Explains almost all Solution behaviors Osmosis – the movement of solvent through a semi- permeable membrane from a region of high solute concentration to low solute concentration. Osmotic Pressure – the pressure created after the system attains equilibrium, calculated by:

Combined with Explains almost all Solution behaviors Semi-permeable membrane: now this is a very special device: selective for molecular size  Size exclusion What is an important example that uses a Semi-permeable membrane? Living cells: have many ways of selecting which molecules get inside or stay outside

Previously in Chem 104: Equilibrium & LeChatelier’s Principle 4 (or 3?) Colligative Properties:  P solv = X solvent P o solvent   T bp = K bp m solute   T fp = K fp m solute  = c R T TODAY Example Calcs Equilibrium and Osmosis Examlette Monday For the Future: Enthalpies Do Not Predict Dissolution— they can be exo- and endothermic