cem181f07e1a - Chemistry 181H Fall, 2007 EXAM I Thursday,...

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Unformatted text preview: Chemistry 181H Fall, 2007 EXAM I Thursday, 27 Sept 2007 WRITE your'Name 4% Student Numb er Recitation Time: Monday There are 7 questions on this exam, worth 15 points each. Write your answer, showing all work to each on each page. A list of potentially useful equations is on page 12. A periodic table is contained on page 13. 4? Aim 1. The element silver has two stable isotopes, one with 60 neutrons and the other has 62 neutrons. You will need information in the periodic table to answer the following two questions. (a) (5 points) Calculate the volume of the lighter silver nucleus in cubic angstroms (Hint: 1 m=101°(A)). i fi’ '5 ID 7: v=r+r°“(%>*(':‘> =- _ EWL . (b) (10 pomts) (Wm the relative abundances of the two lsotopes of silver. wag} = loch + {lama} \o’},%°r 1 loam: + 10'} ~l0?7< 0.8} = H 0.45; '1 75 Aflzfl' \ ‘ A: ‘ 7' WW 2. The following questions refer to the interaction potential between a nitrogen and an oxygen atom. Melting point 63.05 54.8 K First Ionization Potential 1400 1310 kJ/mol 3.0 3.4 —7 —141 kJ/mol 74 66 pm X Pauling Electron Affinity Atomic Radii (a) (5 points) In the space below make a careful sketch of the interac— tion potential between a single nitrogen atom and a single oxygen atom. Be sure to label each axis and that the asymptotic values are qualitatively correct. w s M WM 14% A ll (Mimic, c eds (b) (5 points) Give a concise description of why you would expect the N—O bond to be polarized in terms of fundamental atomic structure. 11:2. Ma’to'XMAuM/lw/A (AL/Am e4 Wapwwa’MMZI-o‘lflzgl mueoni/‘A ) aJL (felM‘a w (c) (5 points) Estimate the percent ionic character of an NO bond. bio—IQ : “0 ih’m + 2.; lag—xx at A49): ’60 4.4 “70% : H» (043 + g‘ (ON a (70/ :- £7ch :2 :1Z 7o 3. (15 points) Use some of the information in following table to make an estimate of the distance, r, at which the KCl ion pair becomes more stable than the neutral, separated K and Cl atoms. Element Melting point First Ionization Potential 336.5 171.6 K 418 1255 kJ/mol 0.82 3.2 —48 349 kJ/mol 138 181 pm X Pauling Electron Affinity Ionic Radii my: VM +(“mfiia5 1. ¢ Aft/2.42:1 [Ale + 44%)“? m = 52’ 427160 A. -1 Z - 4,,ézszDZZJ2, >< (“XI-3 6602x1512,qu A —- VJ 4n” 8.5s4xr‘7—cziiz 19y 5;— >” 317;:- .Xl¢ A: /.6/4é5<l{;’4 M ’ _9\ fineifimfi" ’ 7W “'55 ‘”" MW 4. Give the Lewis structure, the name of the VSEPR 3Dkstructure, and the bond angleéfior the following molecules or molecular ions. (a) (3 points) ozone molecule (03) O 6\ MfaiM=3) kP=L ‘6- /‘ . . ‘ 30-. a the. MM WW .0 ' . h . /b—u:l‘ (Ba/v)" «1.579.014 .¥. Qw‘l’Law. l2¢ (b) (3 points) sulfite anion (803‘) (Kgl hLia‘mo‘Q “MW’QQ A} aw Hm ugh 5 0 v . // /o e ()9an Ila/W H «C\ “”‘ l—l — as; o o (—3 \o‘ @Vl lz¢ (W6 “‘KQ“ «law 5. Give the Lewis structure, the name of the VSEPR 3D/‘structure, and ~ the bond angles at the specified atom in the following moleculesm LCM (a) (3 points) nitrogen atom in nitrite anion (NOE) MM = 5 ) LF= 1— 4m; 8.24;? «NEW X thtm \Z¢o (b) (3 points) sulfur atom in methanethiol (CH38H) I 0 MM“ MPM=4)L—P=Z~ H\ /\ H +22%th (c) (3 points) sulfur atom in thionyl fluoride (OSFg) O z 4' )LP'; 1 F ’4’}: lmhcbwi (d) (6 points) the Lewis structure and two different VSEPR structures for difluoro—oxyxenon (OXeFZ) CD/F «Pm/9:6") kP=Z ) 4%?an I Molt: ,Q-‘F‘ T“ gtarza C9 p 6. Two questions on blackbody radiation. (3.) (5 points) Estimate the surface temperature of a blue-green star that emits a blackbody spectrum that peaks at 460 nm. _ a7 , .44 K T/lm’ .5- \ a“ g "2 T- \,4+W\L r|¢q4"/c-M. a: éZb¢°\§ 6(4wmw"3—; 3 (b) points) Make an estimate of the total power radiated by the surface of the sun in watts. The diameter of the sun is 1.39x109 m, the mean diameter of the earth is 1.27x107 m, the mean earth—sun distance is 1.49x1011 m, and the surface temperature is 5800 K. A. ’3 M 4 imam: C‘,‘\ r» %= Cri— Am ) Arms» W: MT [12 v~ H35“ «14>; 3i— ?: éctws’ »%K4(68¢¢K\ “<83 4 -‘l Mv/ M56 fl. 7):- 3.8G\4M: MW (I); ,5 X‘LIDZGW Z 7. (140mm) The measured lattice energy of BaClg is —2056 kJ/mol and this compound crystalizes in a fluorite lattice that has a Madelung pa— rameter of 2.519 Estimate the lattice spacing parameter for this crystal. View; MA {ME ewmeoél A z' '5 Z ,Z/sbé.x1}b7:;29 :— PA (Mae flfigocm A a : HA 3L,an A We, (wwmpbfig 'L It a = szzmséZE/mn {Z+)(l—>d.(,o$2;cxy$c 7.91? fi/ 4? amaze/w: (.a.¢<cm¢‘=fm\ AM A a saw “3%; (m 72.4' fl ...
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cem181f07e1a - Chemistry 181H Fall, 2007 EXAM I Thursday,...

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