1. 13.4 Mixtures of Volatile Substance Raoult’s Law
Dr. Fred Omega Garces
Chemistry 201
Miramar College

2. Mixing Volatile Liquids
When a mixture is composed of volatile components, then both components will give rise to a vapor pressure.
PT = PA + PB Dalton's Law of Partial Pressure
The vapor pressure from each component follows Raoult’s Law

3. Benzene and Toluene Consider a two solvent (volatile) system
The vapor pressure from each component follows Raoult's Law.
Benzene - Toluene mixture:
Bz = 1 PBz = P°Bz = 384 torr Bz = 0 PBz = 0
Tol = 1 PTol = P°Tol = 133 torr Tol = 0 PBz = 0

4. Raoult's Law: Positive Deviation
Non-ideal Solution
If component A & B possesses weak attractive force, then the components will repel each other and the volatile components will easily vaporize
Positive deviation from Raoult's Law

5. Raoult's Law: Negative Deviation
Non-ideal Solution
If component A & B possesses strong attractive force, then the components will stick to each other and the volatile components will easily vaporize
\ Negative deviation from Raoult's Law