Chem 161-2011 Lecture 25

Chem 161-2011 Lecture 25 - CHEMISTRY 161-2011 LECTURE 25...

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CHEMISTRY 161-2011 LECTURE 25 ANNOUNCEMENTS MISCELLANEOUS Tue, 12/6 Lecture 24 – Ch. 12 Fri, 12/9 Lecture 25 (last lecture) – Ch. 12 Tue, 12/13 Review for final exam (the only Tavss’ review) Fri, 12/16 Final exam; noon – 3 PM Sections 50-52 Van Dyke 211 Sections 53-55 Voorhees Hall 105 FINAL EXAM 240 (out of 725 points) Trend counts 35% = automatic F Do you have a part-time job or are on sport teams?
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RESPONSIBLE FOR This is what you are responsible for in chapter 12: 12.1 Everything 12.2 Everything except the Clausius-Clapeyron equation 12.3 Everything except (a) Closest Packing (ABABAB . . . ; ABCABCA . . .); (b) X-ray diffraction (including Bragg's Law); (c) calculations involving cell dimensions and/or density. 12.4 Everything 12.5 Everything 12.6 Everything 12.7 Everything* *Note that contrary to the syllabus, section 12.7 IS included.
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PLAN FOR TODAY : Chaper 12 - Intermolecular Forces and the Physical Properties of Liquids and Solids Crystal structure Unit cells Packing spheres Closest packing Types of crystals Ionic crystals Covalent crystals Molecular crystals Metallic crystals Amorphous solids Phase changes Liquid-vapor phase transition Solid-liquid phase transition Solid-vapor phase transition Phase diagrams
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A NOTE ON TODAY’S COVERAGE Crystallography Phase diagrams Phase changes Crystallography and Phase diagrams is new to this class. So I’ll make certain to cover it. But the vast majority of Phase Changes has already been covered. Nevertheless, we’ll try to cover phase changes again today.
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Chem 161-2011 lecture 25 6 ET: Intramolecular bonds are much stronger than intermolecular bonds; e.g., H 2 (g) 2H(g) BE=436 kJ/mol; H 2 (l) H2( g ) Hvapn = 0.90 kJ/mol ET: Only ideal gases don’t have intermolecular forces. ET: Discuss each force. Relative S t r e n g t h * Electrostatic interaction (ion-ion interaction) 1000 = charge-charge interaction = ionic interaction Coulomb’s Law: F = k(Q 1 x Q 2 )/r 2 Ion dipole 500 Hydrogen bonding 100 Y,Y’ = N, O or F Y H Y’ ET: Strong bond because very strong dipole-dipole interaction due to electron-naked small H getting close to small strongly electronegative atoms. F = k(Q 1 x Q 2 )/r 2 ; r is small, so force is large. Dipole-dipole interaction** 10*** polar molec. & polar molec. London forces** 1*** non-polar molecules & non-polar molecules, or non-polar molecules & polar molecules. Magnitude of London forces very sensitive to size/MW/surface area because the greater the size the easier the formation of dipoles (i.e., the greater the polarizability). Compare Xe to Ne. More electrons and electrons further from the nucleus make xenon more polarizable. Also, the greater the surface area, the more the contact.
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Chem 161-2011 Lecture 25 - CHEMISTRY 161-2011 LECTURE 25...

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