Intermolecular Forces (l) & (s) phases:1.Molecule-molecule2.Molecule-ion

Suggested Reading:

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 565-567, read the two sections: “Dipole/Induced Dipole Forces” and “London Dispersion Forces: Induced Dipole/Induced Dipole”.

12.1Know the level of intermolecularforces for each state of matter,s, l, g.

Which has the most and which has none?

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Q: What makes molecules “stick” together in the liquid (and solid) state?

A: The opposite ends of their dipoles: opposites attract…..and like polarities “stick” to like polarities.

HH

water dipole

••

••

O-

+

Recall molecular polarity…?

Opposites attract…..and like polarities “stick” to like polarities.

12.2 Know the following intermolecular forces among dissolved molecules and ions in the liquid state

Intermolecular Force Polar ? Example Strength

Induced Dipole- Induced Dipole No-No N2 to N2 Weakest

Dipole-Induced Dipole Yes-No H2O to O2

Dipole-Dipole Yes-Yes Moderate

Regular HCl to HCl

H-Bonding (limited to F, O, N & :Y)

H2O to H2O H2O to NH3

Dipole-Ion Yes-** Strongest

Pg 563, Exc. 5.2-5.4EOC 1, 3, 5, 7, 17

FORCES INVOLVING FORCES INVOLVING INDUCED DIPOLESINDUCED DIPOLES

FORCES INVOLVING FORCES INVOLVING INDUCED DIPOLESINDUCED DIPOLES

Formation of a dipole in two nonpolar IFormation of a dipole in two nonpolar I22 molecules. molecules.

Induced dipole-induced dipoleInduced dipole-induced dipoleInduced dipole-induced dipoleInduced dipole-induced dipole

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FORCES INVOLVING FORCES INVOLVING INDUCED DIPOLESINDUCED DIPOLES

FORCES INVOLVING FORCES INVOLVING INDUCED DIPOLESINDUCED DIPOLES

How can non-polar molecules such as OHow can non-polar molecules such as O2 2 and Iand I22

dissolve in water?dissolve in water?The water dipole The water dipole INDUCESINDUCES a dipole in the O a dipole in the O22 electric cloud. electric cloud.

Dipole-induced dipoleDipole-induced dipoleDipole-induced dipoleDipole-induced dipole

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Different Levels of Molecular Polarity

A

DE

B C

H

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Dipole-Dipole

H-Bonding

H-Bonding

H-Bonding Between Two H-Bonding Between Two Methanol MoleculesMethanol Molecules

H-Bonding Between Two H-Bonding Between Two Methanol MoleculesMethanol Molecules

H-bondH-bondH-bondH-bond

--++

--

H-Bonding Between Methanol and WaterH-Bonding Between Methanol and Water

H-bondH-bondH-bondH-bond--

++

--

H-Bonding Between H-Bonding Between Ammonia and WaterAmmonia and WaterH-Bonding Between H-Bonding Between Ammonia and WaterAmmonia and Water

H-bondH-bondH-bondH-bond

--

++ --

Base-Pairing through H-Base-Pairing through H-BondsBonds

Base-Pairing through H-Base-Pairing through H-BondsBonds

Hydrogen Bonding in Hydrogen Bonding in BiologyBiology

Hydrogen Bonding in Hydrogen Bonding in BiologyBiologyHydrogen bonding and base pairing in DNA.Hydrogen bonding and base pairing in DNA.

See ChemistryNow, Chapter 12See ChemistryNow, Chapter 12

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Ion-Dipole

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CHCH44

CC22HH66

CC33HH88

CC44HH1010

Intermolecular Force Polar ? Example Strength

Induced Dipole- Induced Dipole No-No N2 to N2 Weakest

Dipole-Induced Dipole Yes-No H2O to O2

Dipole-Dipole Yes-Yes Moderate

Regular HCl to HCl

H-Bonding (limited to F, O, N & :Y)

H2O to H2O H2O to NH3

Dipole-Ion Yes-** Strongest

Pg 563, Exc. 5.2-5.4EOC 1, 3, 5, 7, 17

Boiling LiquidsBoiling Liquids

Liquid boils when its vapor pressure equals atmospheric pressure.

Liquid boils when its vapor pressure equals atmospheric pressure.

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4. If external P = 760 mm Hg, T of boiling is the 4. If external P = 760 mm Hg, T of boiling is the

NORMAL BOILING POINTNORMAL BOILING POINT

5. VP of a given molecule at a given T depends on 5. VP of a given molecule at a given T depends on

IM forces. Here the VP’s are in the orderIM forces. Here the VP’s are in the order

C2H5H5C2 HH5C2 HH

wateralcoholether

increasing strength of IM interactions

extensiveH-bondsH-bonds

dipole-dipole

OOO

LiquidsLiquidsSee Figure 12.17: VP versus TSee Figure 12.17: VP versus T

From Chapter 13.6

Know how to interpret phase diagrams

Phase DiagramsPhase Diagrams

TRANSITIONS TRANSITIONS BETWEEN BETWEEN PHASESPHASESSee Section 13.6See Section 13.6

Lines connect all conditions of T and P where Lines connect all conditions of T and P where EQUILIBRIUM exists between the phases EQUILIBRIUM exists between the phases on either side of the line.on either side of the line.

(At equilibrium particles move from liquid to (At equilibrium particles move from liquid to gas as fast as they move from gas to liquid, gas as fast as they move from gas to liquid, for example.)for example.)

Phase Equilibria — Phase Equilibria — WaterWaterSolid-liquidSolid-liquid

Gas-LiquidGas-Liquid

Gas-SolidGas-SolidPLAY MOVIE

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Freezing/Melting

Deposition/Sublimation

Condensation/Evaporation

Phase Diagram for Phase Diagram for WaterWater

Solid Solid phasephase

Liquid phaseLiquid phase

Gas phaseGas phase

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Triple Point Triple Point — Water— Water

At the At the TRIPLE POINTTRIPLE POINT all three phases all three phases

are in equilibrium.are in equilibrium.

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COCO22 Phase Diagram Phase Diagram

COCO22 Phases Phases

Separate phases

Increasing pressure

More pressure

Supercritical CO2

See Figure 13.20