1. 2/2/2018
OBJ: SWBAT calculate the vapor pressure with one and two solutes in the solution.
What is Raoult’s law and what do the variables in the equation represent?
Vapor pressure 2 and 3 video C10.8 vapor pressure at equilibrium and phase change (3rd video)
3rd video

2. Colligative Properties of Nonelectrolyte Solutions
Colligative properties are properties that depend only on the number of solute particles in solution and not on the nature of the solute particles.
Vapor-Pressure Lowering
P1 = X1 P 1
P 1
= vapor pressure of pure solvent
X1 = mole fraction of the solvent
Raoult’s law
If the solution contains only one solute:
X1 = 1 – X2
P 1
- P1 = DP = X2
X2 = mole fraction of the solute

3. 12.7
Calculate the vapor pressure of a solution made by dissolving 218 g of glucose (molar mass = g/mol) in 460 mL of water at 30°C.
What is the vapor-pressure lowering?
The vapor pressure of pure water at 30°C is mmHg. Assume the density of the solvent is 1.00 g/mL.

4. 12.7
Strategy We need Raoult’s law to determine the vapor pressure of a solution. Note that glucose is a nonvolatile solute.
Solution The vapor pressure of a solution (P1) is
First we calculate the number of moles of glucose and water in the solution:

5. 12.7 The mole fraction of water, X1, is given by
The vapor pressure of water at 30°C to be mmHg. Therefore, the vapor pressure of the glucose solution is
Finally, the vapor-pressure lowering (P) is (31.82 − 30.4) mmHg, or 1.4 mmHg.
P1 =  mmHg
= 30.4 mmHg

6. PA = XA P A
Ideal Solution
PB = XB P B
PT = PA + PB
PT = XA P A
+ XB P B

7. stop