f99 midterm I - .1- 14A1F99-1 Baur CHEMISTRY 14A LECTURE...

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Unformatted text preview: .1- 14A1F99-1 Baur CHEMISTRY 14A LECTURE SECTION 1 FALL QUARTER, 1999 ‘ First Midte/rsn Examinatio Friday, October 29. 1999 Name //VW TA: (check one) 7 (LAST) (FIRST) Raquel Hernandez Billy Hu_____________ Sundeep Sethi Kevin Sheran STION NO. I h IN T U TI N 1. There are four questions. Answer each Wag; you may write on the backs of sheets it you need more room, but no loose sheets of paper will be accepted. 2. Your work must be clearly manned and Lemme; credit will not be given for unintelligible reSponses. 3‘ NW must be shown for all computational items; no credit tor merely putting dovVn an answer, even it COWBOY. 4. Make sure that all answers have the appropriate number of 5. Give units for all answers, unless dimensionless. 6. Open book examination. Any written or printed materials may be used. 7. no NOT LIFT THIS COVER SHEET AND BEGIN WORK UNTIL iNSTBUCTED TO DO SO! I w' if H 1.008 O 16.00 M 22.99 Cl 45 Ti 47.88 Br 79.90 He 4.003 F 19.00 Mg 24.30 Ar 39.95 Fe 55.85 A9107.67 C 12.01 Ne 20.18 8 32.06 K 39.10 Cu 63.55 Cd 112.41 N 14.01 Ca 40.08 Zn 65.39 I 126.90 NA (Avogadro’s Number) = 6.022 x 1021 Photon energy (Planck Law): a - hv - hon. c(veloclty of light) = 3.00 x 108 ms-1 h(PIanck's Constant) = 6.63 x 10-34 J5 Bohr formula: En = -2.178 x 1048 .J (22/n2) (2-.- atomic number, i.e. 1 for H, 2 tor He. etc. 1 e.v.(electron volt) = 1.60 x 10-19.] Coulomb energy between two charges 01 and 02;: EC = 2.31 x 10-19.) nm(Q102/r) (O in multiples of the elementary chzge‘ The Wand algggple are on the back of this sheet. CHECK TO MAKE SURE THAT THIS EXAMINATION PAPER HAS FOUR QUESTIONS AND FIVE PA r -2- 14A1F99-1 Name - 1. (30 points) (a) (20 points) An important reaction in the processing of the titanium ore rutile (TiOg) is 3Ti02 + 4C + 6Cl2 —>3TiCI4 + 2002 + 2C0 if you react a mixture of 500.0 g each of Ti02, C and Cl 2 according to this equation, -which is the limiting reagent? Fm 7707;: 47gg+ (2)4500) 3» 77/66 wflp 2 I : 61.25 M // z 79 .98 7 W“ m5 _. 5'00‘0. 7 #/,(7 444/ ' 4.0 / 791414 M 416a; 7-, ELIE—£171-, : 7/ ' ‘ ‘ 70.707 X By W4; 6’ ,Lme/flw mmzz‘mcm 51%; y{.Zé4¢/7702/: ) i WWW We}: /2-rW%/flfmmoé&vzafm& so dubs/~sz AMW‘ -what is the maxnmum mass of TiCl4 which can be produced? K cam/v4 6/; Mam WM " arm/we . / Z _ , maxmw- M 7704’” H : if? I Zag’Wé/p’ Jefzméfidjy, : 3:3-ZMX/4‘71384. #x3§¢r)?m/-l = 5.04m! x /gc/,7ymL/" = 558. f‘ mama». W70 ‘64 (b) (10 points) The reaction of part (a) above is a redox reaction. Assign oxidation numbers to each atom on each side of the reaction, using the usual rules, and state which atom is oxidized and which reduced. LEFT(REAGENT) SIDE RIGHT(PRODUCT) SIDE Atom Oxidation number Atom xidation number Ti +4 Ti + E O ___‘7—__ O L C 0 C +4 MD 4 2.. Cl 0 Cl —- i The atom oxidized is C' ; the atom reduced is ' cg . You may use this space to explain your answers if you wish. -3- 1'4A1F99-1 Name 2. (20 points) (a) (10 points) Find the minimum amount of energy (in J) required to remove the electron from the gs orbital of a hydrogen atom (that is, to ionize a hydrogen atom starting in its 25 state). Use the Bohr formula given on the front page of this exam; or the equivalent formula in the text on p. 17. E _ .3 ‘21/75 ym‘” 3— (EL, .2 . (b) (10 points) A hydrogen atom in its 25 state is ionized by a photon. The escaping electron has kinetic energy 1.50 x 10-19 J. Find the wavelength of the photon. ' -/,y; 3 45757711. E 4— K1 Ufl/WC 72> IONIZ—E ‘ ,1? 3 54am) l¢7+ NEW” 3 ~ 6% WW]??- I €> 4 AC _<éué3K/0_;VT§)(5.OZ></o mg ) A :. éflrx/V’QT W 7 3:86N0’7’M : fiéM' -4- MM F99—1 Name ' 3. (25 points) - (a) (15 points) Below are shown five configurations of the electrons in the valence shell of the N atom. You are to rank them in energy from lowest to highest, excepting any that are impossible. 0) .LL .1. _ (ii) L L _ Ll. 29 2p 29 Lil 2p 2p 2p 23 23 (iii) , I .1. L L (iv) LL LL __ LL 2p 2p 2p L 2p 2p 2p 23 ' 25 (v) LL L _ LL 29 2F) 2p 23 Are any of the e configurations impossible? If so, state which (’ ’2 and explain why it is imp°SSib'e'l§§//¢ M W W M226 42W ‘ (7m 1 ~ Now rank all the [M configurations in order of increasing energy, from LOWEST (ground state) on the left to HIGHEST on the right. If any two have the same energy, so indicate and show them ‘ meme“ ' (i) cud v anew} 12 ("u 43/ ’ ‘ ("i/WWW) 4%,}? J Alia» a / Waméwrk 23:172’0 LOWEST ENERGY =>=>=>=>===>=>=>=> HIGHES ENERG (b) (10 points) The bond dissociation energy of the HCl molecule is 419 kJ mol-1 (text, p. 82). Of course the bond in HCl is partly covalent; but suppose it were ionic? What then would be the bond energy? Calculate the energy of an H+C|- ion pair at a distance apart given by the ionic radius of Cl-, 181 pm = 0.181 nm = 1.81 x 10-10 m (the radius of H+ can be taken as zero for purposes of this calculation). The formula which you need to use is given in the text, p. 55, and on the front page of this examination , L 47* ;.—/26 xii/63— ECOmefi ’ 2‘5. X“) JmM 0: $14051 . _/ . \ ‘Qflt ATWJ fig ‘ 43.!— ’ ’w‘fi‘ 766 we 5:7 «#4 7/26 290 flmmyéoax/MWWJM — -— I g/ . : -7ég 33 (M/ 14A1F99-1 Name 4. (25 points) V 2- (a) (15 points) Consider the three molecular species S F2, SF4 and S 04 . In one of them, the octet,rule mg be satisfied for the central S atom; in one of them, the octet rule cannot be satisfied for the central 8 atom, and in one of them, it is possible to satisfy the octet rule for the central 8 atom but probably better to violate it. To show which is which, give the Lewis diagram for each below, together with a specification of the electron group geometry, skeletal geometry and hybridization of orbitals on S for each. Give just one Lewis diagram for each but state whether any additional resonance forms are possible. Molecule Lewis diagram Electron group Skeletal Hybridization on _S_ geometry geometry 3 (a) 3 F2 , / 5’ \ F" ,1 Emerita/pzm/ ISfiA/T 5P 20 VW e" " 1 ‘~ 3 (b) SF4 _ ‘i $~F BIPYW’DHL ’6: H L, 2 . 6 _ 5 —0% TE/Wfif/DRAI/ W’fim" (C) 304 | l ‘ ‘ / i9 * $72 mew” 36¢ mgeiDWw .. ' " v - M/Th‘tfi WWU'” wfiemlaa? m2 025 2,, Quad , 0UP 196051213593 Lil/774W “ .' g ( N Wye meTIClV/J'TOU ‘9 W W”/ A 0011794, P For which of these molecules is itximpossible to satisfy the octet rule? Explain briefly. g , 5 Am 54We‘ m JWWM, «new l-fifaew e‘jm 4gb} ,. AIM—WWW M/é (b) (10 points) A gas phase diatomic ion denveg érom 02 is studied and found to be paramagnetic and to have a bond energy of about 300 kJ moi-1. Is it most likely to be 022-, 022+, or C24+? Give a brief explanation for your answer. _ " . MUM/4e 52; “WW “Wm EMA/m 94/4. ...
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f99 midterm I - .1- 14A1F99-1 Baur CHEMISTRY 14A LECTURE...

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