1. Warm Up
Calculate the expected vapor pressure at 25oC for a solution prepared by dissolving g of common table sugar (sucrose = g/mol) in cm3 of water. At 25oC, the density of water is g/cm3 and the vapor pressure is torr.
Psoln = CH2OP0H2O
Mole fraction H2O= mol sucrose
35.63 mol mol =
Psoln = (0.9873)(23.76 torr)
= torr
Vapor pressure has lowered from to torr

2. Freezing Point Depression & Boiling Point Elevation

3. Simulation

4. HW
Define Colligative Properties
p. 522 #46 & 60.

5. Non-Ideal Raoult’s Law
What if both liquids are volatile and contribute to the vapor pressure? Occasionally, they will react and produce less pressure than is expected. Ptotal = PA + PB + PC + …

6. Example
A solution is prepared by mixing 5.81 g acetone (C3H6O, molar mass = 58.1 g/mol) and 11.9 g chloroform (HCCl3, molar mass = g/mol). At 35oC, this solution has a total vapor pressure of 260. torr. Is this an ideal solution? The vapor pressure of pure acetone and pure chloroform at 35oC are 345 and 293 torr respectively.
Hint: Calculate expected pressure, compare it to actual.
0.100 mol acetone, mol chloroform
Now, calc mole fractions.
Ptot = (Xacetone)(Poacetone)+(Xchloroform)(Pochloroform)
Ptot = (.500)(345) + (.500)(293)
= 319 torr

7. Example (cont.)
Ptot = (.500)(345) + (.500)(293) = 319 torr This is lower than the 260 torr shown in the experiment. This means there are interactions between the acetone and chloroform in the solution and they are less likely to become a vapor.

8. 11.8 Suspensions and Colloids
Suspensions and colloids are NOT solutions.
Suspensions: The particles are so large that they settle out of the solvent if not constantly stirred.
Colloids: The particles intermediate in size between those of a suspension and those of a solution.

9. Types of Colloids Examples Dispersing Medium Dispersed Substance
Colloid Type
Fog, aerosol sprays
Gas
Liquid
Aerosol
Smoke, airborn germs
Solid
Whipped cream, soap suds
Foam
Milk, mayonnaise
Emulsion
Paint, clays, gelatin
Sol
Marshmallow, Styrofoam
Solid Foam
Butter, cheese
Solid Emulsion
Ruby glass
Solid sol

10. The Tyndall Effect
Colloids scatter light, making a beam visible. Solutions do not scatter light.
Which glass contains a colloid?
colloid
solution

11. HW
Colligative Properties 11.7 wkst