Presentation on theme: "Suggested Reading (from the 7th ed):"— Presentation transcript:
1Suggested Reading (from the 7th ed): 1) Page 380, I suggest you read the first paragraph in section 8.8 if not the entire section. 2) Review Example 8.12 on pg 384 to make sense of why NH3 is more polar than NF3, which at first seems odd. 3) Read the bottom of pg 558 beginning with, “When a polar…” to “…dipole-dipole attraction.” 4) Read three paragraphs on pg 562, starting with “There is an unusually strong…” to “…(Figure 12.7).” 5) On pg , read the two sections: “Dipole/Induced Dipole Forces” and “London Dispersion Forces: Induced Dipole/Induced Dipole”.
9A: Intermolecular forces (attractions): The sticking power between molecules that keep molecules in a solid or a liquid stateKnow the level and types of intermolecular attractions for molecules in the solid & liquid states
10Intermolecular attractions arise because of weak electrostatic attractions between molecules. Electrostatic attractions occur when an electrically positive region is attracted to an electrically negative region. So called dipoles exist in each molecule.
11Asymmetrical distribution of electrically positive region(s) and electrically negative region(s), i.e. dipole(s), are inherent in polar molecules, such as HF & H2O.δ-OHδ+δ-H-Fδ+δ+
12Symmetrical distribution of electrically positive region(s) and electrically negative region(s), i.e. no dipole, are inherent in nonpolar molecules, such as BF3 & CH4.BFCH
13A: Molecules induce dipoles on other molecules Q: If dipoles are needed for electrostatic attractions between molecules to keep them together in the liquid & solid states then how do nonpolar molecules (those without a dipole) “stick” together to form liquids & solids?A: Molecules induce dipoles on other molecules
37The vapor pressure of a given molecule at a given temperature depends on intermolecular attractions. Increasing vapor pressureC2H5wateralcoholetherIncreasing strength of IM attractionsextensiveH-bondsdipole-dipoleObp = 35oCbp = 78oCbp = 100oC
38Boiling Point trends in a Homologous Series CH4C2H6C3H8C4H10CH4CH3CH3CH3CH2CH3CH3CH2CH2CH3