Prelim_2_Review_Answers

Prelim_2_Review_Answers - a. Revuew Sessmn oflason S. Kong...

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Unformatted text preview: a. Revuew Sessmn oflason S. Kong An SAN Q \( <__‘ ) q Wednesday, November 7, 2007 There was once a farmer who tilled the soil every day in great earnest, trying to make a living off of his crops. He and his wife were honest people, waking early in the morning before the first rays of light skimmed across the pond and into the window of his humble home built of dried cedar and stuck together with an ashen tar. And in those early morning hours, the farmer would rouse his wife to greet the morning light and he would stand, his face a mere inches from the transparent glass, refusing to breathe even the slightest amount lest the first morning rays be vanquished forever by the thick fog of moisture upon silicate. 1. Considering the transparency of all visible light to glass, would you expect glass to be a conductor, semiconductor, or an insulator? How can you support this? it would be helpful to draw some bands. Considering flint 31qu cannot“ obSorlO 0N1 Visible. Ii‘jh‘l“) .Hnai Ho‘s We Can make or reasonable Conclusion ‘" ho £0:ch alone should give, SuFFOr'+ 'lD SlQSS being Woe; Mi (Jill-Orv After a length of time, the farmer glanced back at his bed and found his wife no longer supplanted between the sheets. Water rushed through the copper pipes surrounding the interior of his house and steam began to drift across the ceiling from the bathroom to the bedroom. Knowing that soon breakfast would be made, he hurried to the kitchen, stopping in the living room only once to make a passing glance through a blue window. But stopping once was enough; he squinted as he made out three, blue-tinted gentlemen off in the distance, small as specks but brilliantly colored like copper in its second oxidation state. 2. Would you expect this "blue glass" to be a p-type doped glass or a n-type doped glass? How would you explain this? It would be helpful to draw some bands and imagine how light interacts with the bands. (Glass isn’t really "doped" in this way, by the way.) .__ We [Nola w. H is am. “at rev easier to evade. hitter level Ela'lIMSJ / @kre’ filed!” can O‘L’Wb_3fl‘l 7 % 64mg, electrons 0m jump 'figgfig “N1 0930, y of Small energy levels, ,1} A How/tr! We“: is Still Hag, banal jo‘f) «that C‘Olflflo't be h low erw Visith l5 abborbad “HWS' lg ’OvJ gag/{W is 6155:1564} lile enefjcf li‘jln'et' will 9" through? Tm, l Pam l/ i M 0 (Q. l". fi‘fu-lQl J. In the distance, the farmer made out the silhouettes of three men, armed to the teeth with quartz bottles. Their knuckles pressed against the lips of the bottles, each holding one bottle per hand. Without hesitation, the farmer called his wife and he ran to the kitchen, burying his head under the sink. They were after his prized glass pig, awarded for the "Best use of Silicon Dioxide” back in 2005. There was no way the farmer would allow them to take his big pig without a fight. 3. Draw the Lewis Dot structure of Silicon Dioxide, and predict its shape. Note the proper angles and determine the bond order of the Si-O bond. Are there any delocalized electrons? In terms oforbital shapes, why or why not? 5‘02 _> +0+GJ we“. %+ax(b): lb v.6! . 7‘ 5! O (335i: ——7 *le elm-rm 5N1” 010an Si -7 Linear) ‘30 in+€’a¢"l‘7~"5 Bond Order : a “N0 Adorn:le eleclrms, '3] Can be seen as havinj ‘IWD P-orbi’lqls (Jar-li'tifo'l"flj I.“ +90 (JRBWM' Tr'bm‘ls~ rm Hammer} We; Prorbl-lolis ln‘db‘dfl’.) are rep-"mink"? @ é)" Sa‘dl '3 \;- ‘ U’ The three hoodlums, unaware they were noticed, strolled lazily into the farmland. They meandered in their walk, feet lingering, almost waiting to finish each step that the last possible moment. One of them nodded to the other two, and they broke away from him, each one circling around the farmhouse each one in its own way. The third one simply stood there and smiled, quartz bottles resting between each of his knuckles. His peace did not last long, however, for without a moment's hesitation, his two henchmen came running back screaming loudly interspersed with the sound of glass shattering onto the unpaved floor. Emerging from the glassy dust was the farmer, capped in a straw hat and a dry reed stuck between his teeth. The sunlight glanced at the brilliant green bottle in his hand. “I knew this day would come, Sefiorder," said the farmer. “As did I, Farmorphous,” replied the hoodlum. By now, the Seiiorder’s two accomplices had disappeared from sight. 4. Draw the molecular orbital diagram of SiO, pointing out its HOMO and LUMO. (Treat it as a typical diatomic atom without s-p mixing). Predict the bond order. Is this bond order the same as what you described in question 3? Why or why not? 13,0. 2 ielbe‘ — #q.lo,e') 3 (8’2) = :5 sea ‘I ‘ . 3? "fl’ (5145 i l5 “UT {+0 Sam (15 in 0‘: I WQ- 0‘40 see 'ynw" dirtng calmer GI) (@ 4% '\ ' ' ' r '4¥’ M Q "FQIHJ‘ (5c 0 mdecuicj +0 a: _L 3?; 35 \ \ acculle in—Furm‘lr‘m- Mo‘s myslr be rain on L1H; .Hn ‘ HQ ‘ , - ",2 (Qt) t «Cull 6.02 maccue -\0 3st 6 4V'@@ 5 i ,.. . i3") MOW -*.'*f;-.f:L*-' "I know you’ve come for the pig.” The farmer glanced backwards only several feet away where lay a large swine composed entirely of glass, sparkling in the morning sun. The dust from the ground quickly scattered with the passing breeze, creating a miniature whirlwind which swept a path between the two men. "No, you’re wrong!” The hoodlum smiled and threw his quartz bottles at Farmorphous. The farmer lifted his hands, revealing his own glass bottles and knocked the flying projectiles away effortlessly. But it was already too late. Distracted, he noticed the hoodlum revealing a teflon bottle hidden in his coat, the label all too clear to read for a glass- farming Farmer. It read "HF." "I‘ve come to ensure no one can enjoy your filthy pig!” laughed Sefiorder. He let the bottle fly and the transparent fluid flew to its target. The farmer could only watch as the liquid made its way closer and closer to the pig's eyes. 5. Draw the molecular orbital of HF. Note the following energies of the orbitals: [H(1s): -13.6 eV] [F(25): -40.17 eV] [F(Zp): -18.7 eV]. Note the type of bonds involved and where the electron densities are for the molecular valence orbitals. Given (“Ami enermfesj half: draw +0 Sféiie. A J 0 HF has only a fi—boncl. a ll)" ' 0-5" ” c : ragls on warmly: e dansfi 9r . ,. s usyxammnb 6* H ' 21° -% we) 6“ EM) 27’ "nub i; Cen‘iireLA - 3b 6‘ i; b 0"” F (search), _. . , o“ ‘19 F 3: 4’: H 6. The Farmer is scared because HF is able to react with $0; to form Sin, Sisz‘ and water. This etches the glass. If you consider that the two compounds are 26.985 and 19.768 mass percent Si respectively, what is the hybridization and geometries of Si in each compound? 5‘3 ‘7 96-9857. mass 5; 5; F2‘ :7 was 7. mes: '0“ .130! 5 7" “5* F 7 30-232 7.» mass Cl ‘U/ 36’ Q MOhr “din 0": S; H: \Mui 5; 3 Elm}! F lmi ‘5'. 3% mi F {)1 _ {1, 5”: 1- Cexpoml 5‘ odefl (a Q . . _ ' ‘ ‘ ' New _. ISM? 0k 03“} Urey Squ Hiram Laws Dui- 5-\ l e INN; I: ll— 7 Hsp‘m *Mjcmj _. v :I 50 On ofie’hfih‘w mm 33 me. / l\ Mum“. W {5 i -"r‘ 5‘ i3 - F I F am} . “‘ l d ‘ .. H I | o F o ‘ i F '. : éflec‘yun groups :3: +resonance§ l' I . ‘ F f l+ Bkt’ffm gimp: a +e’lrof‘n9di‘6t'l} 5‘73 Mbidizqii'on OCTC‘WAW“ F U fly 5 gap; Sid-Tim .4—4----u—-- 7» lg QUQMA (“fail/ii? With nary a hope in his life, he closed his eyes, too fearful of how his poor pig would be defaced forever. He had worked so hard on it, spending almost seventeen hours a day on it, neglecting his wife and chickens. The former went to bed grumpy; the latter became thin and lost their abilities to lay. As a result, the grumpy bedfellow turned the latter into a scrumptious dinner. His thoughts focused on the sweet, savory aroma of the thin chicken roasted on a fork. He imagined chewing it... Alas! He could forget no more! Farmorphous opened his eyes and found to his surprise that Sefiorder’sjaw was wide open. He turned toward the pig to find it indeed etched away. There was no longer the brilliant sparkle of a pig. Yet, in its stead, he could not believe that standing as a replacement was a magnificent glass etching of bacon and ham on a plate, proudly glimmering in the sun. The HF had run its course and produced instead something so glamorous that Farmorphous and Sefiorder promptly forgot their feud, entered the sculpture into a contest and won first prize for theirjoint venture for the many years of their newly formed friendship to come. Surely, their bond was reforged from hatred to something more strong and stable than an allyl cation molecule. 7. Allyl cation, CHZCHCHZ”, is a very peculiar molecule. Draw a Lewis dot structure of the Allyl cation, indicating all resonance forms, and depict the hybridization of each carbon. n \ /H CHQCHCH; —7 lb v.6 /C-'—"'(‘_.\ GD H_ H C/ each Cor boo {903863365 3 eledrm | . H graces) 30 “than, are, trigmo‘ resonance Ham“ pm; SP2 Whitley}. ll ll SJN uL-lure \ C1/ a ' (“M ‘Mh‘i‘Sl __ ‘ fESOnunCe , > \\ H (.45.. you}. H / C/ - fly l x H 8. Use the fact that Allyl has delocalized electrons to depict a Molecular Orbital diagram displaying the delocalized electron energies only . Next to each energy level drawn, include drawings of the relevant irbitals involved in delocalization, and shade them in according to their relative energies. 5”“ ‘ 0 O ei'ie C—-—c <—-—c loom memoir, wigin O yfibr‘ov’tais (displayed ...
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This test prep was uploaded on 02/15/2008 for the course CHEM 2070 taught by Professor Chirik,p during the Fall '05 term at Cornell.

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Prelim_2_Review_Answers - a. Revuew Sessmn oflason S. Kong...

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