# HW-9 - Rahman, Tarique Homework 9 Due: Nov 6 2007, midnight...

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Rahman, Tarique – 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 – fnd 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 cis - CHCl CHCl. 1. London Forces 2. dipole-dipole 3. None oF these 4. hydrogen bonding 5. London Forces, dipole-dipole, hydrogen bonding 6. London Forces, dipole-dipole correct Explanation: C Cl H C H Cl is polar. 002 (part 1 oF 2) 10 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. 0.63 3. 0 . 39 correct 4. None oF these 5. 0.76 6. 0.24 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 003 (part 2 oF 2) 10 points Which ion will attract a water molecule more strongly? 1. Equal attraction 2. Al 3+ 3. Be 2+ correct Explanation: The attraction oF the Be 2+ ion will be greater than that oF the Al 3+ ion. Even though the Be 2+ ion has a lower charge, its radius is much smaller than that oF Al 3+ , making the attraction greater. 004 (part 1 oF 1) 10 points Which oF the Following cations is likely to be hydrated in compounds? 1. NH + 4 2. K + 3. Li + correct 4. Cs + 5. Rb + Explanation: Li + is the smallest. 005 (part 1 oF 1) 10 points

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Rahman, Tarique – Homework 9 – Due: Nov 6 2007, midnight – Inst: Vandenbout 2 Which of the following compounds is UN- LIKELY to be commonly available and thus not found in the laboratory? 1. Na 2 CO 3 · 10H 2 O 2. BaCl 2 · 2H 2 O 3. CuSO 4 · 5H 2 O 4. La(NO 3 ) 3 · 6HO 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 signiFcant type of intermolecular forces in a liquid sample of ±uoroform (CH² 3 )? 1. covalent 2. ionic 3. hydrogen bonding 4. dipole-dipole correct 5. dispersion 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.
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## This note was uploaded on 02/04/2010 for the course CH 301 taught by Professor Fakhreddine/lyon during the Fall '07 term at University of Texas.

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HW-9 - Rahman, Tarique Homework 9 Due: Nov 6 2007, midnight...

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