11.1 Intermolecular Forces

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    Hydrogen Bonding

    -a super strong dipole-dipole force

    -must have an F-H, O-H, or N-H bond as a pure liquid

    -must only have F, O, N to hydrogen bond with water (or other H-bond donor)

    Dipole-Dipole Forces

    -interaction between molecules having permanent dipole moments

    -the larger the dipole moment, the larger the force

    London Dispersion Forces
    (van der Waals Forces)

    -weak interactions due to a transient (temporary) dipole

    -all molecules have these but is the only force present for nonpolar molecules

    -higher molecular weight, larger surface area, and greater polarizability result in higher London forces

    Ion-Dipole Forces

    -interaction between ions and polar molecules

    -present when ions are dissolved in polar liquids (such as NaCl in H2O)

    INTERMOLECULAR FORCES
    Hydrogen Bonding -a super strong dipole-dipole force
    -must have an F-H, O-H, or N-H bond as a pure liquid
    -must only have F, O, N to hydrogen bond with water (or other H-bond donor)
    Dipole-Dipole Forces -interaction between molecules having permanent dipole moments
    -the larger the dipole moment, the larger the force
    London Dispersion Forces
    (van der Waals Forces)
    -weak interactions due to a transient (temporary) dipole
    -all molecules have these but is the only force present for nonpolar molecules
    -higher molecular weight, larger surface area, and greater polarizability result in higher London forces
    Ion-Dipole Forces -interaction between ions and polar molecules
    -present when ions are dissolved in polar liquids (such as NaCl in H2O)

    Higher Intermolecular Forces Result in:
    ↑ Higher Boiling Pts
    ↑ Higher Enthalpy of Vaporization
    ↑ Greater Viscosity
    ↑ Greater Surface Tension
    ↑ Higher Critical Temperature/Pressure
    ↓ Lower Vapor Pressure

    vapor pressure vs temperature

    In each set choose the molecule which has the greatest overall intermolecular forces?

    CH4
    CH3CH3
    CH3CH2CH3

    CH3F
    CH3CH3
    CH3OH

    CH4
    CH3CH3
    CH3F

    CH3CH3
    CH3F
    CH3CH2CH3