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Intermolecular ForcesIntermolecular Forces  Ion-dipole  Dipole-Dipole  Dipole-Induced dipole  Induced dipole-Induced dipole  Hydrogen Bonding

Induced Dipole- Induced Dipole Forces: Between nonpolar molecules  Trends:

Hydrogen Bonds: Between Molecules with F-H, O-H, or N-H bonds  Trends: C2H6OC2H6O

Which has strongest IMF?Which has strongest IMF? 1.F 2 2.Cl 2 3.Br 2 4.I 2

Which has the strongest IMF? 1.CH 3 CH 3 2.CH 3 OH

Hydrogen Bonding & The Unusual Properties of Water

Boiling Points and Hydrogen BondingBoiling Points and Hydrogen Bonding

Identifying IMF’sIdentifying IMF’s All molecules Polar Hydrogen Bonding Induced dipole (dispersion) Dipole-dipole Hydrogen Bonding Not Hydrogen Bonding Induced dipole (dispersion) Dipole-dipole Nonpolar Induced dipole (dispersion)

Relative Contributions of Different IMFs

What are the most important IMF’s in propane?What are the most important IMF’s in propane? 1.Induced-dipole 2.Dipole-dipole 3.Hydrogen bonding

What are the most important IMF’s in methanol?What are the most important IMF’s in methanol? 1.Induced-dipole 2.Dipole-dipole 3.Hydrogen bonding

What are the most important IMF’s in octanol?What are the most important IMF’s in octanol? 1.Induced-dipole 2.Dipole-dipole 3.Hydrogen bonding

Properties of Liquids Vapor Pressure (volatility) Boiling Point Enthalpy of Vaporization Viscosity Surface Tension

Molecular interpretation of vapor pressure and boiling. Enthalpy of vaporization:

Clausius-Clapyron Equation: Vapor Pressure,  H vap, and T

Graphical Method of Determining Enthalpy of Vaporization

Example 2. What is the mass of water in the air in this lecture hall? 14 m x 5 m x 17 m T = 22 o C Humidity = 43%

Example 3. A 1-L flask of air is at 30 o C and relative humidity of 68%. The flask is put in a freezer and the temperature decreases to 5 o C. What happens?

Surface Tension