10.1 Intermolecular Forces

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Chad's High School Chemistry Master Course

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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 it 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

↓ Lower Vapor Pressure

Indicate which has the greatest IMFs in each set.

CH3OH                                              CH3OH

CH3F                                                  CH3F

CH4                                                    CH3CH2CH2CH3

vapor pressure of water

Adhesion – The attraction of a substance to other substances.

Cohesion – The attraction of a substance with itself.

Capillary Action – The movement of a fluid through a small diameter tube due to adhesion.