105af06_e4_key

105af06_e4_key - Chem 105a Exam 4 Last First Thursday,...

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Unformatted text preview: Chem 105a Exam 4 Last First Thursday, November 16, 2006 Last 4 digits Student ID # __ __ __ __ Professor Stephens Lab TA's Name ‘ Lab Day & time: Major -> Please Sign Below: I certify that I have observed all the rules of Academic Integrity while taking this examination. Signature: INSTRUCTIONS 1. You must show your work to receive credit. 2. If necessary, please continue your solutions on the back of the preceding page (facing you). 3. YOU MUST Use non-erasable ink. 4. There are 9 problems on 10 pages. Please count them before you begin. CHEM 105a EXAM #4 TI-IRUSDAY, NOVEMBER 16, 2006 NOTE!!! DRAW ALL LEWIS STRUCTURES WITH ELECTRONS AS DOTS (CIRCLES) AND _N_Ql: WITH LINES (BONDS) UNLESS SPECIFICALLY ASKED TO DO SO. ANSWERS WITH LINES INSTEAD OF DOTS WILL BE MARKED AS INCORRECT. l. (12 points) For each of the following molecules (i) write the Lewis structure(s) (use dots, NOT lines) (ii) state the geometry of the electron pairs (based on the VSEPR model) (iii) draw and name the structure of the molecule (atoms connected by lines, no lone pairs) t a) PC13 E 9‘"? : P \m i, / \ dakedab (L Q o (9-. ° .. ' hcgmy O O O a a O " _ ,__WWWW CL Q0. V” V W55. 0) SiF4 d)IC15 " in: u u . 03- ‘E 94¢: : u ‘ o0 . ' .a Q .- . \ / . W0Ck¢wd “A u/ I \U. Seven-c, r 2. (15 pts.) Draw the Lewis structures and the 3D geometrical structures arrived at using VSEPR theory for the following molecules. Name the geometrical structures. In each case, state whether the molecule is predicted to have a non-zero or zero dipole moment. a) c120 t . +61%: <1me 0 El ." t. For: a", h‘wahmy '. .0 '3'. . o ' u (9.20 u (L/ \(I. MifihXLL Diem MW '. Nan-2th: Wald-Isl”. b)SO3 .. . . .O .. ‘ :61 0' .... :0: 9.6:. ..°..s-.O: H"§‘ a o o§.. : :u'. :23: 2' (air: osmou S 04%. Noam! Elan." C) TeF4 a. .. F \ > Dceau «My .. NM... ; F 3:. r d)03 o .0... .. a .. .z'o'. . 1Q, 10 0.6 ' ’ .0, 0 o e)P0C13 D;£d.n. MW ‘. ways“ the ;&,'P°,a. 1"ch ammJ9ca-c. 0‘ . ,.. do. ‘9': 900., u ? /‘:"U~ 3. (lSpts.) Using the appended Table of bond energies, calculate AH for the following reactions. [Notez pay careful attention to the s_igp_ of AH!] a) C3H3 + 502 '9 3C02 + 4H20 (propane) A“ '- D (bows We“) -- 2 D (lac/K6! fiwmcé) (D = be“ “’35 PMS“) ... = ch_c_+ 8 DC—H- +- YDO=Q~ gDC""Q((Q'-') "‘ spa-H = (zuczxrt) +(8xu1) + (fxmr) ~(w7‘iq )-(8f%7) - -- zosz K3- b) N2 + 3H2 '9 2NH3 A“: Dug“ +399...“ — CDN-Hv QM + (am/31) —(‘°*3‘l‘) - ‘ = —- \Q‘i k3. c) C2H4 + H20 9 C2H50H (ethylene) (ethanol/ethylalcohol) A“ = DC=Q+ ‘DC-W + ZDQ‘“ ~ DC-C —DC-D - Do-fi- — {DC-4+ 4. (10 points) Draw the molecular orbital energy level diagrams for a) N2 and b) 02. For each molecule, label all the molecular orbitals, show the electronic configuration, calculate the bond order, and state whether the molecule is diamagnetic or paramagnetic. :1)sz ‘ ET * __—-—0';P * .— —— «a! “Hi’ ‘7th {5” 'W’ «2.9 --Hr' «‘2: + ‘u b)02: ET (3.“: Mu- = 3:3: 3 2. .— 5. (10 pts.) Using the molecular orbital model, write electronic configurations for the following diatomic molecules, and calculate the bond orders. State whether the molecules are diamagnetic or paramagnetic. a) Li; E as #62: ‘fl" 62: b) C2 E ~ 3" “W W "t? w 62*:- H 6;: it» C) S2 ..—-——- on? No W63rt‘ Q:— '- Qwo Mu = 2-0.4 L DlPrWA-QVETIL M 6. (8 pts) State the hybridization of the central atom in each of the following molecules: a) PC13 4. e' (do = RM‘AW‘V w 1? {5 $93 k‘WAJ-tg ...—// b) 13' ‘ .. _. '- { '. V .. .o e ‘3 1 ea rs vamutzrd c)SF4 7. (12 pts) What is the hybridization of the C atom(s) in: a) H2CO (formaldehyde) “\ Czo . H“.- z: (5'. c c, m" Mania»: 0' ‘ u/ H M b) CHC13 (chloroform) 8. (10 pts) What types of inter-atomic/inter-molecular/intcr-ionic forces are predominant in the following solids? a) sodium carbonate was-£0631") \omc. b) carbon dioxide (dry ice) mom DUPWWN Q=Q=b “W c) chromium MéTPd-H Cr H- ~86Nl>n~fq e) silicon CQJALEN I C “k9. E Gunman) 9. (8 pts) In each of the following groups of substances, pick the one with the given property. Explain your answer. a) highest boiling point: I-IBr, Kr, C12 “‘0. “4 Como Gm“ NO‘U“ “0.; vow-5V- HLO’RF 0W] Viol/a SW (1) lowest boiling point: CH4, C2H6, C3Hg amok “Mode, W 0‘43 ‘ w W cull 032M; QLKM wz/ULUvJe {fit Whack EWM . LUMAO vs. Table 8.4 - ‘ Single Bonds Multiple Bonds 11—11 432 N—H 391 I—I 149 =C 614 H—F 565 N—N 160 I—Cl 208 C'="C 839 11—0 427 N—F 272 I—Br 175 O=O 495 H—Br 363 N—Cl 200 C=O‘ 745 H—I 295 N—Br 243 S—H 347 C50 1072 _ N—O 201 S—F 327 N=O 607 C-H 413 0—H 467 S—Cl 253 N=N 418 C—C 347 0—0 146 S—Br 218 NEN 941 C—N 305 O—F 190 S—S 266 CEN 891 C—0 358 O—Cl 203 =N ' 615 C—F 485 0—1 234 Si—Si 340 C—Cl 339 Si—H 393 C—Br 276 F—F 154 Si—C 360 C—I 240 F—Cl 253 Si—O 452 C—S 259 F—Br 237 « C1—C1 239 Cl—Br 218 Br—Br 193 'C=O(C02) = 799 ...
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This note was uploaded on 10/26/2008 for the course CHEM 105ALg taught by Professor Bau during the Fall '07 term at USC.

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105af06_e4_key - Chem 105a Exam 4 Last First Thursday,...

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