Homework 08 - Su, Yung Homework 8 Due: Nov 14 2007, 11:00...

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Su, Yung – Homework 8 – Due: Nov 14 2007, 11:00 pm – Inst: FAKHREDDINE 1 This print-out should have 24 questions. Multiple-choice questions may continue on the next column or page – fnd all choices be±ore answering. The due time is Central time. Each question is worth 1 point. 001 (part 1 o± 1) 1 points The temperature at which a liquid boils is the boiling point o± the liquid. The boiling point is an indication o± the submicroscopic ±orces that hold the matter in the liquid state. Water (H 2 O) boils at 100 C. Ethanol (C 2 H 6 O) boils at 78 C. Ammonia (NH 3 ) boils at - 33 C. Which one o± the ±ollowing ranks the sub- microscopic ±orces in these liquids ±rom the strongest to the weakest? 1. water, ammonia, ethanol 2. ammonia, ethanol, water 3. ethanol, water, ammonia 4. water, ethanol, ammonia correct Explanation: High boiling points result ±rom strong in- termolecular ±orces and low boiling points are indicative o± weak intermolecular ±orces. 002 (part 1 o± 1) 1 points Which response includes all o± the ±ollowing substances H 2 , CH 4 , NH 3 , SiH 4 , HF that can exhibit strong hydrogen bonding, and no others? 1. NH 3 , SiH 4 , and HF 2. H 2 , NH 3 , and SiH 4 3. NH 3 and HF correct 4. H 2 , CH 4 and SiH 4 5. CH 4 and HF Explanation: H-bonds are a special case o± very strong dipole-dipole interactions. They only occur when H is bonded to small, highly electroneg- ative atomes – F, O or N only. In this list, only NH 3 and HF exhibit hydrogen bonding. H 2 , CH 4 , and SiH 4 would exhibit only dispersion ±orces. 003 (part 1 o± 1) 1 points Hydrogen bonds are really just a very strong ±orm o± dipole-dipole interaction. 1. False 2. True correct Explanation: Permanent dipole-dipole interactions are stronger than London ±orces and occur be- tween polar covalent molecules due to charge separation. H-bonds are a special case o± very strong dipole-dipole interactions. They only occur when H is bonded to small, highly electroneg- ative atoms – F, O or N only. 004 (part 1 o± 1) 1 points Which o± the ±ollowing can be expected to exhibit the strongest hydrogen bonding in the liquid state? 1. CH 3 OCH 3 (dimethyl ether) 2. CH 3 OH (methyl alcohol) correct 3. CH 3 COCH 3 (acetone) 4. CH 3 CH 3 (ethane) 5. CH 4 Explanation: H-bonds are a special case o± very strong dipole-dipole interactions. They only occur when H is bonded to small, highly electroneg- ative atoms – F, O or N only. The structure is
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Su, Yung – Homework 8 – Due: Nov 14 2007, 11:00 pm – Inst: FAKHREDDINE 2 H C H H O H Methyl alcohol is the only molecule given that has H bonded to N, O, or F (O in this case). 005 (part 1 of 1) 1 points Which of the following statements about dis- persion forces is NOT correct? Dispersion forces 1. are also called London forces. 2.
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This note was uploaded on 04/15/2009 for the course CH 54740 taught by Professor Fakhreddine during the Spring '09 term at University of Texas at Austin.

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Homework 08 - Su, Yung Homework 8 Due: Nov 14 2007, 11:00...

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