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CHEMISTRY 185
I.
Introduction
II.
Syllabus
III.
Review Chem. 180
A. Lewis Structures, Molecular Geometry,
and Molecular Polarity
IV.
Let’s Rock! - Intermolecular Forces (Chp. 12)
A. Types of Intermolcular Attractive Forces
1. Van der Waals
2. Relative Strengths of Attraction
B. States of Matter and Physical Properties
1. Liquids
2. Solids
3. Phase Diagrams
C. Structure and Bonding in Solids
1. Types of Crystalline Solids
2. Structure of Crystalline Solids
D. Read and Study on Your Own
What makes a liquid a liquid, a
solid a solid, and a gas a gas?
III.
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Review Chem. 180
A. Lewis Structures, Molecular Geometry,
and Molecular Polarity
Which of following compounds has the highest
boiling point?
C4H10 or (CH3)2CO
Need - polarity of molecule
(and therefore shape)
Examples
PCl5
C4H10
(CH3)2CO
http://www.tapplastics.com/uploads/products/Acetone-xl.jpg, http://i.dailymail.co.uk/i/pix/2014/11/17/video-undefined-233DC32400000578708_636x358.jpg, http://www.sciencealert.com/images/stories/2011-Oct-Dec/Magnascan_-_boiling_water.jpg
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IV.
Intermolecular Forces
Focus on inter not intra-molecular forces
inter = between different molecules
intra = within the same molecule
What impact do I.M.F. have on chemical compounds?
Physical Properties
Expand? Flow?
Solid
Liquid
Gas
Compressible?
Rate of
Diffusion
I.M.F.
Johannes Diderik van
4 der Waals
A.
Types of Intermolcular Attractive Forces
1. Van der Waals Attractions
i.
ii.
iii.
iv.
London Dispersion
Dipole – Dipole
Hydrogen “Bonds” (special type of dipole-dipole)
Other
How are the particles attracted to each other?
Attraction between two charged or partially charged
particles
i. London Dispersion Forces (LDF)
(named after Fritz London)
- attractions due to instantaneous or induced dipoles
https://www.learner.org/courses/physics/visual/img_lrg/fritz_london.jpg, http://www.nobelprize.org/nobel_prizes/physics/laureates/1910/waals_postcard.jpg
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Which Molecules -
Comparative Strength of LDF -
What affects polarizability?
http://www.chem.ucla.edu/~harding/IGOC/D/decane01.jpg
1-Chlorodecane
b.p. = 223ºC
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1-Decanol
b.p. = 233ºC
ii. Dipole-Dipole
Which Molecules?
Comparative Strength of dipole-dipole
Which of the following has the largest boiling point?
C6H6, C6H5Cl, or C6H5OH
http://www.chem.ucla.edu/~harding/IGOC/D/decane01.jpg, http://www.chemeddl.org/alfresco/d/d/workspace/SpacesStore/5776a5e3-4b84-4651-96673ffed239a9f5/1-chlorodecane-jmol.jpeg?guest=true
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iii. Hydrogen “Bonds”
Which Molecules?
-
H-Bonds occur when:
F-H -- :OO-H -- :OF-H -- :NO-H -- :NF-H -- :FO-H -- :FWhy so strong?
Example of H-bonding
http://blogs.scientificamerican.com/compound-eye/files/2013/09/trigona3.jpg
N-H -- :ON-H -- :NN-H -- :F-
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H-Bonding and the Density of H2O
H2O
H 2O
Parafin Wax
H2O(s)
d = 0.9150 g/cm3
H2O(l)
d = 1.0000 g/cm3 (4ºC)
= 0.9982 g/cm3(20 ºC)
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Example Problem
Oil of wintergreen, or methyl salicylate, has a melting point
of -8C. Methyl-4-hydroxybenzoate is a different molecule with
exactly the same molecular formula yet it has a melting point of
127 C. Based on the structures given below, use a combination
of words and pictures to explain the large difference in melting
points for the two compounds.
O
O
C OCH 3
C OCH3
OH
OH
Oil of wintergreen
m.p. = -8C
Methyl-4-hydroxybenzoate
m.p. = 127C
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iv. Other Types of Non-Covalent Attractions
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2. Relative Strength of Intermolecular Forces
Useful when trying to compare which pure
compound in a group of compounds has a certain
physical property (eg. Highest b.p. or m.p., etc)
LDF < dipole-dipole < H-bonding < ion-dipole < < ionic
N2
HCl
NH3
Na+ in H2O
NaCl
General Rules
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Example Problems
Rank the following in order of increasing B.P.
HI, HCl, HBr, HF
Which member of the following pair has the
lowest MP?
1. NaCl or HCl
2. NH3 or PH3
3. Xe or I2
4. cis-dichloroethene or trans-dichloroethene
b.p. = 60.3ºC
b.p. = 48.0ºC
https://upload.wikimedia.org/wikipedia/commons/a/ad/Trans-1%2C2-dichloroethene.png
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B. States of Matter and Physical Properties
1. Liquids
a.
b.
c.
d.
Viscosity
Surface Tension
Vapor Pressure and Enthalpy of Vaporization
Other Physical Properties
a. Viscosity –
Example:
Which is more viscous?
Hexane – CH3CH2CH2CH2CH2CH3
Or
Nonane – CH3CH2CH2CH2CH2CH2CH2CH2CH3
http://www.cdn.sciencebuddies.org/Files/6782/6/falling-ball-viscometer-dimensions.JPG
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b. Surface Tension -
Interior Structure of Glass
i.) cohesion –
Si O
O
Si O
O
Si O
O
Si O
Interior Structure of Glass
ii.) adhesion –
Si O
O
Si O
O
Si O
O
Si O
 Capillary action
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Equilibrium – “a state of balance between opposing
forces or actions that is either static or
dynamic”
c. Vapor Pressure Fraction of Molecules
Lower Temperature
Higher Temperature
Minimum energy needed to
Escape
Kinetic Energy
What impacts vapor pressure?
http://community.berghaus.com/wp-content/uploads/2014/11/wetting1.jpg, http://community.berghaus.com/wp-content/uploads/2014/11/bead.jpg ,
http://artofembodiment.com/wp-content/uploads/2010/08/Pic_See-saw_XSmall_opt.jpg , http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/imgkin/vapp3.gif ,
http://www.globalresearch.ca/wp-content/uploads/2013/06/RevolvingDoor.jpg
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Enthalpy of Vaporization (∆Hvap) - the amount of energy in the
form of heat that must be
added to vaporize a certain
amount of liquid at constant
temperature (kJ/mol)
What impacts ∆Hvap ?
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Classius Clapyron Equation
P2
∆Hvap
P1
R
ln ( ) =-
1
1
( - )
T2 T1
d.Other Physical Properties
Normal Boiling Point:
Critical Point:
http://myshinykitchen.com/wp-content/uploads/2011/05/All-American-Pressure-Canner-915.jpg
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2. Solids
Melting
Freezing
Sublimation
Deposition
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3. Phase Diagrams
Want
- a “map” that tells us what phases (i.e. solid, liquid,
or gas) of a substance will be stable under certain
temperatures and pressures
Need
1.
2.
1. Phase changes
solid  liquid
liquid  solid
 melting
 freezing
-
liquid  gas
gas
 liquid
 vaporization
 condensation
-
solid
gas
 gas
 solid
 sublimation
 deposition
http://wps.prenhall.com/wps/media/objects/3311/3391416/imag1104/AAAUAZI0.JPG, https://ocjewishexperience.files.wordpress.com/2010/02/uci.gif
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2. At what temperature and pressure is each phase
present?
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Phase diagram
-
Phase Diagram Terms
normal b.p. –
normal m.p. –
triple point –
critical temp. –
critical pressure –
critical point –
supercritical fluid –
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What does the slope of the solid-liquid line tell us?
https://s-media-cache-ak0.pinimg.com/236x/03/b7/51/03b75117b7e72dd03bb1fb0048cc775c.jpg,
http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/Articleimage/2003/CP/b305555h/b305555h-f1.gif
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Example problem
What happens as we move from A-E and from 1-3?
Things to be careful of when looking at phase diagrams and
comparing them to nature.
http://wps.prenhall.com/wps/media/objects/3311/3391416/imag1104/AAAUAZI0.JPG, https://ocjewishexperience.files.wordpress.com/2010/02/uci.gif ,
http://www.cem.msu.edu/~mantica/cem152/prep1/carbon_pd.gif, http://d32ogoqmya1dw8.cloudfront.net/images/research_education/equilibria/h2o_phase_diagram__color.v2.jpg
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C. Structure and Bonding in Solids
Solids
Crystalline –
.
Amorphous –
1. Types of Crystalline Solids
a. Molecular -
b. Covalent Network-
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c. Ionic Solids-
d. Metallic Solids-
https://www.webelements.com/_media/elements/crystal_structure_image/K-bs.jpg
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2. Structure of Crystalline Solids
lattice -
unit cell-
http://s3.amazonaws.com/kidzworld_photo/images/2014129/93f1a038-7254-4186-be25-73c0786bd8fb/salt-crystals-article.jpg
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Structure of Crystalline Solids Cont’d
Close Packing -
Two Types
1. Hexagonal Close packing (hcp)
2. Cubic Close Packing (ccp)
Vocabulary
Coordination Number -
The number of particles
immediately surrounding a
particle in the crystal
structure
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Hexagonal Closed Packed (ABAB)
Cubic Closed Packed (ABCABC) FCC
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Cubic Unit Cells and #’s of atoms
Cubic Unit Cells -
Position
Center (or inside)
Face
Edge
Corner
Fraction in Unit
Cell
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What can we do with this information?
1. Determine density, atomic radius,
atomic weight, etc.
2. Determine empirical formula.
1. Cobalt is composed of face centered cubic unit
cells. Assuming that cobalt has an atomic radius
of 125 pm, calculate the density of solid cobalt.
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2. The cubic unit cell for a pure compound composed
of atoms A and B is shown below. What is the
formula for the compound?
http://advances.sciencemag.org/content/2/7/e1600319.full,
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3. If the density of the compound in the problem
above is 7.5 g/cm3, what is the length of an edge
of the cubic unit cell (in appropriate units)?
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D. Read and Study on Your Own
1. X-Ray Diffraction (Pg 535-537)
2. Lattice Energy (Pg 542-544)