1. Warm Up
How many milliliters of 18.4 M H2SO4 are needed to prepare mL of 0.10 M H2SO4?
M1V1 = M2V2
1.8 mL
2.7 mL
3.3 mL
4.0 mL
4.6 mL
(18.4 M)(V1) = (0.10 M)(600.0 mL)
V1 = 3.26 ~ 3.3 mL

2. Warm Up
A flask contains 0.5 mol of SO2(g), 1 mol of CO2(g) ,and 1 mol of O2(g). If the total pressure in the flask is 750 mmHg, what is the partial pressure of SO2(g)?
750 mmHg
375 mmHg
350 mmHg
150 mmHg
Dalton’s Law
P = sum of partial pressures of each gas
# mol = = 2.5 mol
750 mmHg = 300 mmHg
2.5 mol mol
SO2 = 0.5 mol x 300 mmHg = 150 mmHg
mol

3. Warm Up (mass fraction)

4. Vapor Pressure William Henry Francois Marie Raoult
(2:16)
(19:02)

5. Henry’s Law
The concentration of a dissolved gas in a solution is directly proportional to the pressure of the gas above the solution
Applies most accurately for dilute solutions of gases that do not dissociate or react with the solvent
Yes  CO2, N2, O2
No  HCl, HI

6. Raoult’s Law Psolution = Observed Vapor pressure of
The presence of a nonvolatile solute lowers the vapor pressure of the solvent.
Psolution = Observed Vapor pressure of
the solution
solvent = Mole fraction of the solvent
P0solvent = Vapor pressure of the pure solvent
Addition of nonvolatile solute will cause the vapor pressure to fall in direct proportion to the mole fraction of the solute.

7. Simulation

8. Example
A solution is prepared by dissolving grams of hexane, C6H14, in grams of benzene, C6H6, Calculate the mole fraction of benzene in the solution described above. The vapor pressure of pure benzene at 35oC is 150.mmHg. Calculate the vapor pressure of benzene over the solution described above at 35°C.
.3469 mol C6H =
Psoln = (.9089)(150. mmHg) = 136 mmHg

9. Liquid-liquid solutions in which both components are volatile
Modified Raoult's Law:
P0 is the vapor pressure of the pure solvent
PA and PB are the partial pressures

10. Raoult’s Law – Ideal Solution
A solution that obeys Raoult’s Law is called an ideal solution

11. Negative Deviations from Raoult’s Law
Strong solute-solvent interaction results in a vapor pressure lower than predicted
Exothermic mixing = Negative deviation

12. Positive Deviations from Raoult’s Law
Weak solute-solvent interaction results in a vapor pressure higher than predicted
Endothermic mixing = Positive deviation