Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:09 PM
Copyright © 2016 Dan Dill [email protected]
Lecture 13 CH101 A1 (MWF 9 am)
TP Whichofthefollowingareassociatedwithintramolecularforces
forceswithin amolecule ?
13%
13%
13%
13%
13%
13%
13%
13%
1.
2.
3.
4.
5.
6.
7.
8.
Friday, October 7, 2016
Fogformsonacoldmorning
Wetclothesarehungouttodry
Icemelts
1and2
1and3
2and3
Alloftheabove
Noneoftheabove
• Complete:Vaporpressureandboiling
• Intermolecularforces
Nextlecture:Hydrogenbonding;dipole‐dipoleinteraction polarity ;
dispersioninteraction;relativeboilingpoints
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Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
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Copyright © 2016 Dan Dill [email protected]
Liquid-vapor equilibrium
Copyright © 2016 Dan Dill [email protected]
Equilibrium vapor pressure
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Copyright © 2016 Dan Dill [email protected]
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
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Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:09 PM
Copyright © 2016 Dan Dill [email protected]
Equilibrium vapor pressure
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Equilibrium vapor pressure
Low temperature
⟶Few particlesinvapor
⟶Low equilibriumvaporpressure
Higher temperature
⟶More particlesinvapor
⟶Higher equilibriumvaporpressure
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Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Copyright © 2016 Dan Dill [email protected]
Equilibrium vapor pressure
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Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Liquid-vapor equilibrium
Normalboiling temperature
⟶Maximum particlesinvapor
⟶1atm equilibriumvaporpressure
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Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:09 PM
Copyright © 2016 Dan Dill [email protected]
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
TP Theorderofnormalboilingpointsis lowesttohighest …
Vapor pressure and boiling point
Substance
The normal boiling point is the temperature at which bubbles form at 1 atm.
Can we make bubbles (and so “boil”) at a lower temperature?
Let’s see …
20%
20%
20%
20%
20%
1.
2.
3.
4.
5.
Vaporpressure
at25˚C,kPa
Acetone,CH3C O CH3
30.8
Diethylether, CH3CH2 2O
71.7
Ethanol,CH3CH2OH
7.87
Water,H2O
3.17
Copyright © 2016 Dan Dill [email protected]
100
diethylether acetone ethanol
ethanol acetone diethylether
acetone diethylether ethanol
ethanol diethylether acetone
somethingelse
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Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Normal 1atm boilingpoint ˚C
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
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Copyright © 2016 Dan Dill [email protected]
Vapor pressure and boiling point
Relative normal boiling point, Tb
Thenormalboilingpointisthetemperatureatwhichbubblesform at1atm.
Thenormalboilingpointisthetemperatureatwhichbubblesformat1atm.
Whatdoyoupredictforrelativenormalboilingpointsofthesesubstances?
Substance
Vaporpressure
at25˚C,kPa
Normal 1atm boilingpoint ˚C
Acetone,CH3C O CH3
3:30.8
3:56
Diethylether, CH3CH2 2O
4:71.7
4: 35
Ethanol,CH3CH2OH
2:7.87
2:78
Water,H2O
1: 3.17
1.100
Whatdoyoupredictforrelativevaporpressuresofthesesubstancesat 200
°C?
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Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:09 PM
Copyright © 2016 Dan Dill [email protected]
Quiz Thesubstancewiththelowestvaporpressuresubstances
at 200°C is…
25%
25%
25%
25%
1.
2.
3.
4.
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Enthalpy change of vaporization, ∆vapH
H2O l ⇌ H2O g ,ΔvapH 40.7kJ/molat100˚C
NH3 l ⇌ NH3 g ,ΔvapH 23.3kJ/molat 78˚C
N2 l ⇌ N2 g ,ΔvapH 5.6kJ/molat 196˚C
etc.
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Copyright © 2016 Dan Dill [email protected]
TP Whichofthefollowingiscorrectaboutwater?
20% 2.
20% 3.
20% 4.
20% 5.
Copyright © 2016 Dan Dill [email protected]
CH4
NH3
HCl
N2
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20% 1.
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Intramolecular and intermolecular forces
Thelowenthalpyofvaporizationresultsinalowvaporpressure
atroomtemperature
Thehighenthalpyofvaporizationresultsinalowvaporpressure
atroomtemperature
Thelowenthalpyofvaporizationresultsinahighvaporpressure
atroomtemperature
Thehighenthalpyofvaporizationresultsinahighvaporpressure
atroomtemperature
Thereisnosimplerelationshipbetweenvaporpressureand
enthalpyofvaporization
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Intermolecularforcesareforcesofattractionbetweenmolecules
Chemicalchangesarerelatedtobreakingandformationofcovalentbonds due
tointramolecularforceswithinmolecules.
Physicalchangesaregovernedbyintermolecularforces
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Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:09 PM
Copyright © 2016 Dan Dill [email protected]
TP Whichofthefollowingareassociatedwithintramolecularforces
forceswithin amolecule ?
13%
13%
13%
13%
13%
13%
13%
13%
1.
2.
3.
4.
5.
6.
7.
8.
Copyright © 2016 Dan Dill [email protected]
Intermolecular forces: stickiness!
Amoleculesattractoneanother,becauseoftheattractionofoppositeelectrical
charges.
Fogformsonacoldmorning
Wetclothesarehungouttodry
Icemelts
1and2
1and3
2and3
Alloftheabove
Noneoftheabove
Mostspecificandstrongest is“hydrogenbonding”:X—H∙∙∙Y
Morecommonandintermediatestrengthis
“dipole‐dipoleattraction”:
Alwayspresentandweakest is“temporarydipoleattraction”
“dispersioninteraction” :
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Lecture 13 CH101 A1 (MWF 9 am) Fall 2016
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