Polarity of Bonds and Molecules
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Transcript of Polarity of Bonds and Molecules
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Polarity of Bonds and Molecules
Mrs. Huelin ChemistryApril 24,
2012
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Polarityof bonds …HCl
H2O
of molecules …H2O
CO2
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For each molecule, draw the Lewis structure, predict the shape and bond angle, and identify as polar or nonpolar. Br2
HCN
C2H2
NH4+
H2S
PF3
CH2O
MgO
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Electronegativity differences indicate Polarity
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Electronegativity difference (∆En) and Bond type
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For each pair of elements, calculate the electronegativity difference and label the bond type (polar covalent, nonpolar covalent, or ionic).H, ClH, SS, ClNa, FCl, BrAl, Br
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Energy Practice ProblemGiven the following bond
dissociation energy values, calculate the total energy that would be required to break all of the covalent bonds in 0.25 mol of ethane (C2H6).
C-C = 347 kJ/molC-H = 393 kJ/mol
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VIDEO LESSONWater, a polar molecule, on YouTube:
http://www.youtube.com/watch?v=DVCYlST6mYQ
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REVIEWIonic and Covalent CompoundsPractice Quiz and Graphics:
http://www.elmhurst.edu/~chm/vchembook/145Areview.html
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Internet resourcesMolecular polarity:
http://www.elmhurst.edu/~chm/vchembook/210polarity.html
Polar covalent compounds: http://www.elmhurst.edu/~chm/vchembook/152Apolar.html
Nonpolar covalent compounds: http://www.elmhurst.edu/~chm/vchembook/150Anpcovalent.html
Ionic compounds: http://www.elmhurst.edu/~chm/vchembook/143Aioniccpds.html
Compare Ionic, Polar, and Nonpolar Bonds: http://www.elmhurst.edu/~chm/vchembook/153Acompare.html
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Properties of Covalent CompoundsLow melting and boiling points
(melting sugar, not salt)Many exist as gases or vaporize
readily at room temperature (oxygen, carbon dioxide)
Form relatively soft solids (paraffin wax)
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Forces of Attraction Intramolecular
forces (bonding forces)
Covalent bond is strong (sharing of electrons)
Covalent network solids = brittle, nonconductors, extremely hard, very high melting point (diamond, quartz)
Intermolecular forces (a.k.a. van der Waals forces)Dispersion (induced dipole)
= between nonpolar molecules
Dipole-dipole = between polar molecules
Hydrogen bond = between hydrogen on one molecule and fluorine, oxygen, or nitrogen on another
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Multiple Choice Review1. Which
substance contains both covalent and ionic bonds?
a) NH4NO3
b) CH3OCH3
c) LiFd) CaCl2
2. Which of
these bonds is most polar?
a) H-Clb) H-Brc) H-Fd) H-I
3. Which of these molecules can form a hydrogen bond with a water molecule?
a) N2
b) NH3
c) O2
d) CH4