hw 9 answers - Iype Shelby Homework 9 Due Nov 6 2007...

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Iype, Shelby – Homework 9 – Due: Nov 6 2007, midnight – Inst: Vandenbout 1 This print-out should have 23 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. Room Assignments for EXAM 2 A-K WEL 1.316 L-O WEL 2.122 P-Z WEL 1.308 001 (part 1 of 1) 10 points Identify the kinds of intermolecular forces that might arise between molecules of N 2 H 4 . 1. hydrogen bonding 2. dipole-dipole 3. London forces 4. None of these 5. London forces, dipole-dipole 6. London forces, dipole-dipole, hydrogen bonding correct Explanation: N H H N H H is polar. 002 (part 1 of 2) 10 points 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 . 35 correct 2. 0.52 3. 0.76 4. 0.63 5. None of these 6. 0.24 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 003 (part 2 of 2) 10 points Which ion will attract a water molecule more strongly? 1. In 3+ correct 2. Ca 2+ 3. Equal attraction Explanation: The attraction of the Ca 2+ ion will be less than that of the In 3+ ion because it has both a larger radius and a lower charge. 004 (part 1 of 1) 10 points Which of the following cations is likely to be hydrated in compounds? 1. NH + 4 2. Rb + 3. K + 4. Li + correct 5. Cs + Explanation: Li + is the smallest. 005 (part 1 of 1) 10 points Which of the following compounds is UN- LIKELY to be commonly available and thus not found in the laboratory?
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Iype, Shelby – Homework 9 – Due: Nov 6 2007, midnight – Inst: Vandenbout 2 1. BaCl 2 · 2H 2 O 2. Na 2 CO 3 · 10H 2 O 3. La(NO 3 ) 3 · 6HO 4. CuSO 4 · 5H 2 O 5. KCN · 2H 2 O correct Explanation: K + is only a +1 cation AND it is too large to substantially attract waters of hydration. +2 and +3 cations will generally form hydrates. Na + will also attract water due to its smaller size. 006 (part 1 of 1) 10 points What would be the most significant type of intermolecular forces in a liquid sample of fluoroform (CHF 3 )? 1. hydrogen bonding 2. dispersion 3. ionic 4. covalent 5. dipole-dipole correct 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.
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