Exam 2-solutions - Version 298 Exam 2 mccord (50970) 1 This...

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Unformatted text preview: Version 298 Exam 2 mccord (50970) 1 This print-out should have 34 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. McCord CH301 001 10.0 points Consider the following pairs A and B A 1 ) N N O b b b b b b b b A 2 ) N N O b b b b b b b b B 1 ) P O O O O b b b b b b b b b b b b b b b b b b b b b b 3 B 2 ) P O O O O b b b b b b b b b b b b b b b b b b b b 3 of Lewis structures. Select the one from each pair that is likely to make the dominant contribution to a reso- nance hybrid. 1. A 2 and B 2 2. A 1 and B 1 3. A 1 and B 2 4. A 2 and B 1 correct Explanation: A 1 ) N N O b b b b b b b b- 1 +1 A 2 ) N N O b b b b b b b b +1- 1 The second structure is preferred because it places the negative formal charge on the most electronegative atom. B 1 ) P O O O O b b b b b b b b b b b b b b b b b b b b b b- 1- 1- 1 3 B 2 ) P O O O O b b b b b b b b b b b b b b b b b b b b- 1- 1- 1 3 The first structure is preferred for the same reason. 002 10.0 points The electronic arrangment is the same as the molecular shape when 1. there are no lone pairs of electrons on the central atom. correct 2. there are more shared electrons than non- shared electrons. 3. the molecule is not polar. 4. the number of bonding orbitals equals the number of anti-bonding orbitals. 5. the atoms are joined by sigma bonds. Explanation: The only time that the molecular shape and electronic arrangement are the same is when there are no lone pairs of electrons on the central atom. 003 10.0 points Which of the following would have the highest melting point? 1. KF correct 2. KI 3. KBr 4. KCl 5. RbF Explanation: KF has the highest charge density. 004 10.0 points The energy diagram in this question is the molecular orbital diagram for a homonuclear diatomic molecule. The lines represent MOs but the labels have been removed. Consider the following molecular orbital di- agram: Version 298 Exam 2 mccord (50970) 2 a b c What are the names of the labeled orbitals, a through c, respectively? 1. 2 p , 2 p , 1 s 2. 2 p , 2 p , 1 s 3. 2 p , 2 p , 1 s correct 4. 2 p , 2 p , 2 s 5. 2 p , 2 p , 2 s Explanation: 005 0.0 points EXTRA CREDIT QUESTION: A re- minder here to PLEASE bubble in your name, uteid, and your version number correctly. Do it now - dont wait till the end of the exam. Also, a reminder that there is NO CLASS tomorrow (Friday, October 8th). Thats right, you get to SKIP chemistry class. Ill see you on Monday, the 11th, and well start up on Chapter 5....
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This note was uploaded on 10/23/2010 for the course CH 50970 taught by Professor Dr.mccord during the Fall '10 term at University of Texas at Austin.

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Exam 2-solutions - Version 298 Exam 2 mccord (50970) 1 This...

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