HW08-solutions-QUY - arriaga (yga77) HW08 quy (50970) This...

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arriaga (yga77) – HW08 – quy – (50970) 1 This print-out should have 31 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points What would be the most signifcant type oF intermolecular Forces in a liquid sample oF ±uoroForm (CH² 3 )? 1. dipole-dipole correct 2. hydrogen bonding 3. dispersion 4. covalent 5. ionic Explanation: London Forces, dispersion Forces, van der Waals or induced dipoles all describe the same intermolecular Force. London Forces are in- duced, short-lived, and very weak. Molecules and atoms can experience London Forces be- cause they have electron clouds. London Forces result From the distortion oF the elec- tron cloud oF an atom or molecule by the presence oF nearby atoms or molecules. Permanent dipole-dipole interactions are stronger than London Forces and occur be- tween polar covalent molecules due to charge separation. H-bonds are a special case oF very strong dipole-dipole interactions. They only occur when H is bonded to small, highly electroneg- ative atoms – ², O or N only. Ion-ion interactions are the strongest due to extreme charge separation and occur between ionic molecules. They can be thought oF as both inter- and intramolecular bonding. CH² 3 is a polar molecule that does not con- tain H bonds; thereFore, dipole-dipole Forces will be the most signifcant type oF intermolec- ular Forces present. 002 10.0 points ²orces between particles (atoms, molecules, or ions) oF a substance are called 1. intramolecular Forces. 2. armed Forces. 3. intermolecular Forces. correct 4. None oF these Explanation: Bonds within molecules or Formula units are called intramolecular Forces. Bonds between particles are called intermolecular Forces. 003 10.0 points Which oF the Following structures represents a possible hydrogen bond? 1. Br H · · · Br 2. Cl H · · · Cl 3. C H · · · O 4. ² H · · · ² correct Explanation: H-bonds are a special case oF very strong dipole-dipole interactions. They only occur when H is bonded to small, highly electroneg- ative atoms – ², O or N only. 004 10.0 points IdentiFy the kinds oF intermolecular Forces that might arise between molecules oF Br 2 . 1. hydrogen bonding 2. None oF these 3. London Forces correct 4. London Forces, dipole-dipole, hydrogen bonding 5. London Forces, dipole-dipole 6. dipole-dipole Explanation:
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arriaga (yga77) – HW08 – quy – (50970) 2 Br b Br b b is non-polar. 005 (part 1 of 2) 10.0 points Calculate the ratio of the potential energies for the interaction of a water molecule with an Al 3+ ion (of radius 53 pm) and with a Be 2+ ion (of radius 27 pm). 1. 0.52 2. 0.24 3. 0.63 4. 0 . 39 correct 5. 0.76 6. None of these Explanation: r Al = 53 pm r Be = 27 pm The energy E p -| z | μ r 2 , so the ratio is E Al E Be = | z Al | r 2 Be | z Be | r 2 Al = | 3 | (27 pm) 2 | 2 | (53 pm) 2 = 0 . 389284 006 (part 2 of 2) 10.0 points Which ion will attract a water molecule more strongly? 1.
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This note was uploaded on 01/30/2012 for the course CHEM 301 taught by Professor Wandelt during the Spring '08 term at University of Texas at Austin.

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HW08-solutions-QUY - arriaga (yga77) HW08 quy (50970) This...

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