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HW08 Quy - perlick(app582 HW08 quy(50970 This print-out...

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perlick (app582) – HW08 – quy – (50970) 1 This print-out should have 31 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0points What would be the most significant type of intermolecular forces in a liquid sample of fluoroform (CHF 3 )? 1. dispersion 2. dipole-dipole correct 3. ionic 4. covalent 5. hydrogen bonding 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 – F, 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. CHF 3 is a polar molecule that does not con- tain H bonds; therefore, dipole-dipole forces will be the most significant type of intermolec- ular forces present. 002 10.0points Forces between particles (atoms, molecules, or ions) of a substance are called 1. None of these 2. intermolecular forces. correct 3. intramolecular forces. 4. armed forces. Explanation: Bonds within molecules or formula units are called intramolecular forces. Bonds between particles are called intermolecular forces. 003 10.0points Which of the following structures represents a possible hydrogen bond? 1. F H · · · F correct 2. Br H · · · Br 3. Cl H · · · Cl 4. C H · · · O 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 – F, O or N only. 004 10.0points Identify the kinds of intermolecular forces that might arise between molecules of HF. 1. London forces, dipole-dipole, hydrogen bonding correct 2. None of these 3. dipole-dipole 4. London forces, dipole-dipole 5. London forces 6. hydrogen bonding Explanation:
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perlick (app582) – HW08 – quy – (50970) 2 H F is polar. 005(part1of2)10.0points Calculate the ratio of the potential energies for the interaction of a water molecule with a Ca 2+ ion (of radius 100 pm) and with an In 3+ ion (of radius 72 pm). 1. 0.24 2. 0.63 3. None of these 4. 0.52 5. 0.76 6. 0 . 35 correct Explanation: r Ca = 100 pm r In = 72 pm The energy E p -| z | μ r 2 , so the ratio is E Ca E In = | z Ca | r 2 In | z In | r 2 Ca = | 2 | (72 pm) 2 | 3 | (100 pm) 2 = 0 . 3456 006(part2of2)10.0points Which ion will attract a water molecule more strongly?
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