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Unformatted text preview: .1 14A1F991 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 ms1 h(PIanck's Constant) = 6.63 x 1034 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 1019.] Coulomb energy between two charges 01 and 02;: EC = 2.31 x 1019.) 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
14A1F991 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
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' 4.0 / 791414 M
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‘ 70.707 X By W4; 6’ ,Lme/ﬂw mmzz‘mcm 51%; y{.Zé4¢/7702/: ) i WWW We}: /2rW%/ﬂfmmoé&vzafm& so dubs/~sz AMW‘ what is the maxnmum mass of TiCl4 which can be produced? K
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= 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
1'4A1F991 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 1019 J. Find the wavelength of the photon. ' /,y; 3 45757711. E 4— K1 Uﬂ/WC 72> IONIZ—E
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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 mol1 (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 1010 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—
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(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
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For which of these molecules is itximpossible to satisfy the octet rule? Explain briefly. g , 5 Am 54We‘ m JWWM, «new
lﬁfaew 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 moi1. 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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