1.6 Intermolecular Forces
CHECK OUT CHAD'S
PRE-HEALTH PREP
PRE-HEALTH PREP
Table of Contents
Add a header to begin generating the table of contents
Intermolecular Forces
| 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) |
How to Rank Boiling Points
| Ranking Boiling Points |
|---|
| 1) Network Covalent (Cdiamond , SiO2) |
| 2) Ionic |
| 3) Hydrogen Bonding |
| 4) Dipole-Dipole (if all molecules are similar in size) |
| 5) London Forces |
| Higher Intermolecular Forces Result In |
|---|
| Higher Boiling Points |
| Higher Melting Points |
| Greater Viscocity |
| Greater Surface Tension |
| Lower Vapor Pressure |
Effects of Branching on Melting Points and Boiling Points
Branching (usually) decreases the boiling pt, but increases the melting pt
Solubility
“Like dissolves like.” (in terms of polarity)