#Chem 161-2006 Exam III + Answers

#Chem 161-2006 Exam III + Answers - Dr. E. Tavss 12/01/06...

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Dr. E. Tavss 12/01/06 CHEM 161-2006 EXAM III + Answers HILL & PETRUCCI CHAPTER 8 – ELECTRONIC CONFIUGATION, ATOMIC PROPERTIES, AND THE PERIODIC TABLE PERIODIC TABLE AND PERIODIC PROPERTIES MAGNETIC PROPERTIES PARAMAGNETISM AND DIAMAGNETISM 1. Which of the following would you expect to exhibit paramagnetism ? I. Fe II. S III. Cr 2+ IV. Kr A. all of the above. B. II, III and IV C . I, II and III D. I, II and IV E. II and III. Noble gases have all electrons paired. Plot electron configuration beyond the noble gas core. Paired electrons are very weakly diamagnetic. Unpaired electrons are strongly paramagnetic. A single unpaired electron more than nullifies the effect of many paired electrons. 26 Fe = [Ar]4s 2 3d 6 Unpaired electrons = paramagnetic 16 S = [Ne]3s 2 3p 4 Unpaired electrons = paramagnetic 24 Cr 2+ = [Ar]4s 2 3d 4 → [Ar]4s 1 3d 5 → [Ar]4s 0 3d 4 = [Ar]3d 4 Unpaired electrons = paramagnetic 36 Kr = [Ar]4s 2 3d 10 4p 6 All paired electrons = diamagnetic CHEM 161-2006 EXAM III Chem 161-2006 Exam III + Answers 1 ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓ ↑↓
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RESONANCE 2. Which ones of the following pairs represent resonance structures? (NOTE: formal charges on individual atoms are not shown). I. B F F F B F F F II. H C C H O H H C C H O H H H III. N N O N N O IV. H C N H N C A. I, III and IV. B . I and III. C. I, II and III. D. II and IV. E. II, III and IV. Resonance definition Same Equal amounts of the same atoms, i.e., isomers. Atoms bonded to the same atoms Same number of electrons Different Different arrangement of the electrons I. Yes. Fits the above definitions. II. No. Not all of the atoms are bonded to the same atoms. In the isomer on the left the O is bonded to an H and a C. In the isomer on the right the O is only bonded to a C. (This particular arrangement of isomers is known as tautomers.) III. Yes. Fits the above definitions. IV. No. Not all of the atoms are bonded to the same atoms. In the isomer on the left the C is bonded to a H and a N. In the one on the right the C is only bonded to a N. CHEM 161-2006 EXAM III Chem 161-2006 Exam III + Answers 2
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STRUCTURES RESONANCE 3. Which of the following structures represents the BEST Lewis structure for NOCl? A. N O Cl A. B. O Cl N B. C. Cl N O C. D. Cl N O D. E . O N Cl E. Note: Not all of the electrons in these structures show on my computer monitor. If you, also, are having difficulty, print out this page. The electrons are visible on hard copy. Note: The written name, “NOCl”, is not meant to suggest that N is connected to O is connected to Cl, just as H 2 SO 4 is not meant to suggest that two hydrogens are attached to each other in that molecule. To write Lewis structures, put the least electronegative element in the middle.
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This test prep was uploaded on 04/12/2008 for the course CHEM 161 taught by Professor Vacillian during the Fall '08 term at Rutgers.

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#Chem 161-2006 Exam III + Answers - Dr. E. Tavss 12/01/06...

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