To Do…
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Electronic homework (Lon-Capa)
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Review Sessions
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HW8 Type 1: due Wed., April 30 by 7 pm
Exam 3 review: due Wed., April 30 by 7pm
Tuesday: 161 Noyes Lab; 6:00-7:50 pm
Wednesday: 161 Noyes Lab; 8:00-9:20 pm
Exam #3: Thursday, May 1, 7 pm
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114 David Kinley Hall
Intermolecular Forces (IMFs)
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London Dispersion Forces
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London dispersion forces
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All molecules exhibit these forces.
Due to temporary and induced dipoles.
Strongest IMFs for non-polar molecules
Examples include nitrogen (N2) and
methane (CH4).
With more electrons, more chance of an
induced dipole.
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Dipole-dipole interactions
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Dipole-dipole interactions
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Polar molecules exhibit these forces.
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(also exhibit LDFs)
Due to permanent dipoles.
Stronger IMFs than LDFs (given similar
sized molecules).
Some polar molecules (such as H2O)
exhibit a special kind of dipole-dipole
interaction.
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Water is a Liquid!
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Hydrogen Bonding in Water
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Clicker Question
How many of the following interactions does
CH3CH2CH3 exhibit?
London dispersion
dipole-dipole
hydrogen bonding
A) 0
B) 1
C) 2
D) 3
Clicker Question
How many of the following interactions does
CH3CH2OH exhibit?
London dispersion
dipole-dipole
hydrogen bonding
A) 0
B) 1
C) 2
D) 3
Clicker Question
How many of the following interactions does
CH3OCH3 exhibit?
London dispersion
dipole-dipole
hydrogen bonding
A) 0
B) 1
C) 2
D) 3
Clicker Question
How do you think the molecules rank with
respect to boiling point?
A) CH3CH2CH3 > CH3OCH3 > CH3CH2OH
B) CH3CH2CH3 > CH3CH2OH > CH3OCH3
C) CH3CH2OH > CH3CH2CH3 > CH3OCH3
D) CH3CH2OH > CH3OCH3 > CH3CH2CH3
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Ion-ion interactions
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Ionic compounds exhibit these forces.
Due to ions.
Strongest of the IMFs (given similar sized
molecules).
Example includes sodium chloride (NaCl).
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Clicker Question
Which of the following molecules exhibits
dipole-dipole interactions?
a) OF2
b) SF6
c) XeF4
d) C2H2
e) At least two of the above molecules (a-d)
exhibit dipole-dipole interactions.
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Clicker Question
Which of the following molecules would be
expected to have the lowest boiling point?
a) C4H10
b) NH3
c) H2O
d) C2H6
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Clicker Question
Methane (CH4) is a gas, but carbon tetrachloride
(CCl4) is a liquid at room conditions. Which of
the following explains this phenomenon?
a) CCl4 is a polar molecule and CH4 is not.
b) CCl4 and CH4 have different geometries and shapes.
c) CH4 exhibits hydrogen bonding and CCl4 does not.
d) Cl is more electronegative than H.
e) None of the above explanations explains this.
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Clicker Question
Which of the following molecules would be
expected to have the highest melting
point?
a) CO2
b) N2
c) SO2
d) H2
e) H2O
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