Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:10 PM
Copyright © 2016 Dan Dill [email protected]
Lecture 14 CH101 A1 (MWF 9 am)
TP Whichofthefollowingmoleculesarenot polar?
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2.
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4.
5.
6.
Tuesday, October 11, 2016
BFCl2,whoseshapeistrigonal‐planar,likethatofBF3
SCl2,whichisabent molecule,likeH2O
NH2Cl,whoseshapeistrigonal‐pyramidal,likethatofNH3
OCS,whichisalinear molecule,likeCO2
Alloftheabovearenonpolar
Alloftheabovearepolar
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Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
• Hydrogenbonding
• Dipole‐dipoleinteraction polarity
Nextlecture:Dispersioninteraction;relativeboilingpoints;solvation
inionicsolutions;solubilityrules memorizesolubilityguidelinesfig
6.28p181 ;ionizationofmolecularsolutes;self‐ionizationofwater;
precipitationreactions
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Intermolecular forces: stickiness!
Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Hydrogen bond angle is 180°
Amoleculesattractoneanother,becauseoftheattractionofoppositeelectrical
charges.
Mostspecificandstrongest is“hydrogenbonding”:X—H∙∙∙Y
Morecommonandintermediatestrengthis
“dipole‐dipoleattraction”:
Alwayspresentandweakest is“temporarydipoleattraction”
“dispersioninteraction” :
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Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:10 PM
Copyright © 2016 Dan Dill [email protected]
Hydrogen bonds are longer than typical bonds
Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Which of the following can form H bonds?
• Ammonia,NH3
• Methanol,CH3OH
• Ethanol,CH3CH2OH
• Dimethylether,CH3OCH3
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Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Quiz Whichofthefollowingcannot formhydrogenbondswiththemselves?
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13%
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13%
1.
2.
3.
4.
5.
6.
7.
8.
Ammonia,NH3
Methanol,CH3OH
Ethanol,CH3CH2OH
Dimethylether,CH3OCH3
1and3
1and4
2and4
Alloftheabovecanformhydrogenbondswiththemselves
0 of 0
Copyright © 2016 Dan Dill [email protected]
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Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
Dipole-dipole attraction
Moleculesmustbe“polar”
Whatmakesamoleculepolarisunequalsharingofelectronclouds.
Sharingtendencyisproportionaltoelectronegativitydifference.
Thegreaterthedifference ofelectronegativities,
themoreunequalthesharing,
themorepolarthesharedelectroncloud.
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Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:10 PM
Copyright © 2016 Dan Dill [email protected]
Electronegativity χ: Relative pull
Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
The more different the χ’s, the more polar the bond
• Iftwobondedatomsaredifferent,theonewithlargerχ getsmoreofthe
sharedelectroncloud
• Atomwithlargerχ hasnetnegative charge;atomwithsmallerχ hasnet
positive charge
• Thelargerthedifferenceinχ,thegreaterthechargeseparation unequal
sharingofelectroncloud
• Resultisapolarbonds
Thelargerχ themorepiggish theatom
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Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
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Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
Copyright © 2016 Dan Dill [email protected]
TP Whichofthefollowingmoleculesarenot polar?
Molecular polarity
• Ifbonddipolescancel,moleculeisnonpolar
• Ifbonddipolesdonotcancel,moleculeispolar
17%
17%
17%
17%
17%
17%
1.
2.
3.
4.
5.
6.
BFCl2,whoseshapeistrigonal‐planar,likethatofBF3
SCl2,whichisabent molecule,likeH2O
NH2Cl,whoseshapeistrigonal‐pyramidal,likethatofNH3
OCS,whichisalinear molecule,likeCO2
Alloftheabovearenonpolar
Alloftheabovearepolar
Let’sillustrate,forBF3 andBH2F
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Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
Lecture 14 CH101 A1 (MWF 9 am) Fall 2016
2/6/2017 1:10 PM
Copyright © 2016 Dan Dill [email protected]
Quiz Whichofthefollowingstatementsistrueaboutcarbondioxide,O C O?
25% 1. Carbondioxidecontainspolarbondsandisapolarmolecule
25% 2. Carbondioxidecontainspolarbonds,butisnotapolarmolecule
25% 3. Carbondioxidedoesnotcontainpolarbondsandisnotapolar
molecule
25% 4. Carbondioxidedoesnotcontainpolarbondsbutisapolarmolecule
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