contemplated with

Combined with

Explains almost all Solution behaviors

We saw three examples of Colligative Properties:colligative – depends only on the number of particles

Tfp = Kfp msolute

Tbp = Kbp msolute

Psolv = Xsolvent Posolvent

Tfp = Kfp msolute

Tbp = Kbp msolute

Psolv = Xsolvent Posolvent

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 ---------------------------------------------------- 2.00

Ideal behavior, no association of ions ---------------------------------------------------- 3.00

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

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Semi-PermeableMembrane bag

5% sugarsolution

This is the system at equilibriumThis is what createsthe dis-equilibriumIn the beaker

pasta marshmallow nut

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The system is disturbed away from equilibrium

X H2O(outside) ≠ X H2O(inside)

100% H2O(outside) ≠ 95% H2O(inside)

The system will respond by shifting equilibrium

H2O(outside) H2O(inside)

How???

Only water molecules can move thorough membrane

The membrane is invisible to water

pasta marshmallow nut

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When the system responds by shifting equilibrium:

If diluted to 1% sugar:

0.00278 mol/ 0.095 L = 0.0293 MUsing:

= c R T

= 0.0293 M x 0.082057 atm/M K x 298 K

= 0.716 atm or 544 mm Hg

The sugar solution under pressurerises up the tube, like a manometer.

The height represents the Osmotic Pressure

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Waterfills beaker

corn syruppipet fits tightly into

hole

core of carrot

removed and filled

withcorn syrup

CarrotAs amembrane

pasta marshmallow nut

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= 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 specialdevice: 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:

Psolv = Xsolvent Posolvent

Tbp = Kbp msolute

Tfp = Kfp msolute

= 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