chem200 f06 Beauvais exam3c

chem200 f06 Beauvais exam3c - CHEM 200 Exam 3C November 29,...

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Unformatted text preview: CHEM 200 Exam 3C November 29, 2006 Name __I I s___s . h Lab Sect. No. I? (Print) Last First Signature: - 1 (Sign) 4‘" I ~- *****Important: Please mark C under Test Form on your scantron sheet!***** This exam consists of a Question 1:' where you indicate which exam form you for 1 point, 0_ Questions 2726: the 25 test questions worth 6 points each= 0 Questions 27—28: harder, extra~credit problems worth 6 points each, for a total of 163 possible points. Make sure that your test has all 9 pages including this cover sheet and the attached periodic table/exam information sheet. Please read each problem carefully. There are no intentionally misleading questions; each problem should be taken at its face value. Please mark your answers BOTH on your scantmn sheet and on the essam itelf. You may use the designated Casio fx‘300ms—plus calculator during the exam. Use the back pages of the test as scratch paper. You are not allowed to use any textbooks, notes, or homemade reference sheets during the exam. Cell phones and other communication devices are absolutely not to be available during the exam. These must be deactivated and put out of reach for the entire exam period. Students found with any such device accessible during the exam may be required to forfeit the exam. You may leave if you finish the exam early. Give the exam and the information sheet to your TA and leave quietly without disturbing other students. Before leaving, check that all your answers have been properly entered on the scantron sheet and the exam and that your name is written on every page of the exam and on the scantron sheet and that you filled in the correct Test Form designation C on your scantron sheet. Exam scores will be posted on Blackboard as soon as the grading is complete. Your test will be returned to you in the first lab meeting of next Week. If you have any questions regarding the grading of your exam, please notify your TA. The time available for the exam is 100 minutes. Good luck! . Mark answer “C” on your scantron form for 1 point and to ensure that your exam is correctly graded. . Identify the main group to which X belongs in the ionic compound formula NaX. Group 1 (b) Group 2 (c) Group 16 ((1) Group 17 (e) Group 3,000,000 . Which of the following has the bonds correctly arranged in order of decreasing po— larity (i.e.— from most polar to least)? (a) Mg—F > Be—F > 0-1? > N—F (b) or > Be—F > Mg—F > N—F (c) Mg-F > Be~F > N-F > 0-1? @io—F > N-F > Be—F > Mg—F (e) penguin > polar bear > arctic fox . Which of the following best describes the type of bonding you would expect for the bond in FCl: ' (a) ionic (b) metallic nonpolar covalent (cl) polar covalent (e) duct tape . Which of the following ionic solids would you expect to have the highest lattice enthalpy? (a) BaO (b) 0501 (Q) SrO (d) BaClg (e) 0520 6. Which of the following lists the bonds in order of increasing bond length? (a) C~N < C=N < C=O r (b) C=0 < C:N < C—N. (c) C—N < C=O < C=N (d) 020 < C—N < C=N (é) CzN < 020 < CAN 7. Which of the following molecules has the longest C—O bond? (You may need to draw the Lewis structures to answer this question.)*\ U .' l, ‘53 005' 1 . 2;. 2,1; =2 '. t: (b) C02 ‘ ' I (C) CO p H \w- ', IX}, (d) They all have the same C—O bond length ‘. \ ;‘. Q o - (e) None of these molecules actually exists. 8. Which is the most important resonance structure for laughing gas, N20? (Formal charges age not given.) " l ' r l. . II o. igzNzo HiNEN—QI ~—— :rSI—Nao: ’\ x3 I *1; r\ C ‘y‘ (e) It may be called laughing gas, but I find nothing amusing about this question. 9. Which of the following is the best description of the orbitals on each atom that we overlap to make the NEN triple bond in the N2 molecule? ta) an sp hybrid and two unhybridized p orbitals on each N atom. '1 (b) three unhybridized p orbitals on each N atom. (c) an unhybridized s orbital and two unhybridized p orbitals on each N atom. (d) two 3102 hybrids and one unhybridized p orbitals on each N atom. (8) three 3193 hybrids on each N atom. 10. Which of the following should be the best Lewis structure for cyanoaeetylene? a) :\\l C) .. Hfi Cécxtc= N H— ciao: C: 1}; e) H—b—éfi— CE N b) d) %=C:C:C:N@ H-CEC— CE N 11. Estimate the heat of reaction for 02H2(9l + 2142(9) —’ C2H6(9) using only the following bond energies (all in kJ/mol): : "l P7 . Q ‘_ t \32 .n f“, “’x "L4 J) l“ ’\ ' . - v v\ (a) 4660 M i) i; ' “l {\‘i :{Q} —296 kJ ‘ y ‘ \ (c) ~—728 kJ ' N;- (d) 1389 kJ - i (e —116() M U“ ‘ l - q 12. Given these electronegativities, F 4.0 O 3.5 Ci 3.0 L ‘9'; N 3.0 C 2.5 H 2.1 which of the following is true? The N—Cl bond is stronger than the NwF bond. (pd/In the F0 molecule, the bond dipole arrow points towards the O atom. The C—CI bond is ionic. (CU/The H—Cl bond is more polar than the OeH bond. (e) None of the above is true. 44} h. T‘ / 13. One resonance structure is drawn below for one form of the amino acid glycine. Which of the following correctly lists the formal charges at the atoms? H H ( N(+1), 03(0), cb(0),oa(~1), ohm) (5) N(0), Ca(+1), 023(0), 04-1) Ob("1) (C) N(+1), 03(0), Chm): 040), 0b(—1) ewe). Cam), Cb(+1), 04-1), 013(0) “Tammyoa(+1),cb(+i),oa(—1),ob(—1) 14. Consider the two isomers HNC and HCN. Which one is more stable and why? H-“NECfi vs- H—CENi e a 0 (a’ijN C is more stable because the more electronegative N is the central atom. HCN is more stable because it has lower formal charges on its atoms than HNC. (C) HNC is more stable because it has lower formal charges on its atoms than HCN. (dz/HON is more stable because the more electronegative C is the central atom. It really depends on what the definition of “is” is. 15. The Cl—C-Cl bond angle in CC14 is: < i. - “:3 f l (a) exactly 90° k g exactly 109.50 a g _ Y . (c) slightly greater than 1096" ‘ (Cl) exactly 120° (8) exactly 451°F 16. Given the correct Lewis structure of the expanded octet molecule XeClF (below), what best describes the Cl—XefiF bond angle in XeClF? D X? ‘ < 90° exactly 90° c) exactly 120° d) exactly 180° ) (e > 180° 17. What is the molecular shape of C52? t‘ ‘. ‘2 .4 1‘... - .I l (a) trigonal pyramidal 3:- ' (b) trigonal planar I .‘ ‘- r ,2; (‘ : (c) bent ’ " v linear twisted (e) H ‘A 18. Of H4, CH3Cl, CHQCIQ, CHCl3, and (3014: {ED only CH3C1 and CHC13 are polar. (b) only CH4 and COL; are polar. (c) only CH4 and CCl4 are nonpolar. (d) only Cchl and CHC13 are nonpolar. (6) only CH2C12 is nonpolar. 19. If T‘ng has a square pyramidal shape, how many lone pairs are on the central Te atom? ‘ l (a) 0 a i. ‘ t J... {E 1 ‘ \ A; _. " (c) 2 t | ‘ u I (d) 3 _ g (e) 4 I l ‘ '. I 20. What are the hybridizations of the two carbons in CHgCFg? (a) one is 3p2 and the other is 3393 H : 3 (b) one is 3p and the other is 3232 E ’r II, (0) both are SP3 [ w 1 both are Sp2 H - z (e) both are Sp 21. The bonds in ketene, with Lewis structure sketched below, cam be classified as (a) 2 or bonds and 2 7r bonds (b) 3 or bonds and 3 7r bonds ((3) 4 0 bonds (8) 4 0 bonds and 2 7r bonds (e) 6 0' bonds 22. How many carbons in one molecule of benzaldehyde (shown below) have a trigonal planar shape? (a) 0 (b) 1 (c) 3 (d) 5 @7 23. What is the average bond order of each N—O bond in the nitrite anion, NOE? (You L, . " \ may need to draw the Lewis structure(s) to answer this question.) i l} '2 1.". W. (a) 1 (b) 4/3 °° - ' 'o x.- z r»: r-i o a a (c) 3/4 ‘ _ M U“ . is to; 3/2 i ; W2 24. Which of the following correctly describes the heat flow of the sample q and the change in temperature AT during vaporization: (a1 9 is positive and AT is zero *(‘Ifi-q is zero and AT is positive @ q and AT are both positive (qu and AT are both zero (6) q = r AT I 25. If the heat of vaporization of water is 40.7 kJ/mol. How man}r grams of water'at 100.0°C evaporate when 20.0 M of heat are absorbed? _ i ‘- N i I, <a>0.491g BB W .30“ ii wMXlU " ’ (b) 8.85 g ' V I) a (c) 0.366 g Al I f {it ‘--.I,r' ((1)0.0273 g v - 'l ' (e) 2.04 g 26. The molar heat capacities of methanol ar 81.6 J K‘1 rnol‘1 for the liquid and £3.89 .TK”1 mol—lifor the gas, and the heat : aporlzation is 3 .21 kJ/mol. We begin if] . mol of methanol gas at an initial temperature of lwand cool the sample to 2.00 mol of liquid at 646°C, which is the normal boiling point. What is the overall AH for the process? V C I E, a fl“w%€i¢d ..~ (a) 39.6 M *t“ (b) 16.3 M g. ' J v\ (c) —8850 M - i ' i (d) —79.2 kJ ) (e —6l.6kJ — VHLW 59::j [\2.Wt~l)(©' lULi'Ubl xwfiifi fi/‘UAl Sk¢)g‘21)tz\ ‘igg+ing ntuildlviifl 27. Extra credit problem. The lattice enthalpy in this problem is defined as a positive number, the enthalpy for the reaction ionic solid _) separated gas—phase ions. Which of the following expressions is equal to the lattice enthalpy for magnesium bromide: (a) AHf(MgBr) + AH” (Mg) + AH‘fi’apBr) vap + IE1(Mg) + IE2(Mg) + Ema) (b) »AHf(MgBr) + AHE..(Ms) + Mam/1g) + ammo» + amass) + IE1 (Mg) + IE2(Mg) + gsmerg) (c) —AH.«(MgBr2) + Man/1g) + AHsapng) + amass) + 1313mm) + IE1(Mg) + IE2(Mg) + 2 EA(Br) (d) AHdMgBr'z) + AHfilJMg) + AHSap(Ms) + AHEJJBM) + AHiap(Br2) + BE(Br2) + IE1(Mg) +1E2{Mg) + 2 EA(Br) (e) —AHf(MgBr2) + swam/1g) + AHgfimrg) + AH3aP(Br2) + BE(Br2) + IE1(Mg) + IE2(Mg) + was») 28. Extra credit problem. A sample of dry ice (solid C02) at its normal sublimation temperature of —78.5°C in a closed container is transformed to CO; gas by the addition of 100.0 mL of liquid water at 250°C. All of the dry ice sublimes into 002 gas, and 50.0 mL of the water freezes into ice. The final temperature of the water and the C02 is 00°C. Find the mass of the 002, given that 6002(9):0.843 J Kvl g—l, CH20{1)=4.184 J K_1 gwl, Angb’cofzsns kJ/mol, AHpust20=ao2 kJ/mol. (a) 157 g (b) 68.6 g (c) 165 g (d) 42.5 g. (e) none of the above CHEM 200 Exam/Quiz Information Sheet Physical Quantities atomic mass unit (amu) : 1.66056‘x 10—27 kg Avogadrds number = 6.022 x 1023 universal gas constant (R) = 8.314 J/K-mol = 0.08206 L-atm/K-mol absolute zero : —273.15 0C 2 0K specific heat capacity of water (CHzo) : 4.184 J/g°K speed of light (c) = 3.000 x 108 m/s Planck’s constant (k) : 6.626 x 10—3‘l J-s Conversion Factors 131m = 1.01325 x 105 Pa : 1.01325 bar : 760 tort 1 calorie = 4.184 J Ijoule : 1 kg-rr12/s2 Equations PV : nR T PA :XA X Ptotal d : (molar mass! x P RT 3RT u . : —"—— mm molar‘mass AE I q + w Mm“ : ZAHOf(products) — ZAHth‘eactants) heat capacity : q/AT specific heat capacity (c) : q/(mass x AT) speed oflight (C) : v x Tm Ephoton : hV 3 LC 7L Eelsctron : X 10718 X [22/142] Affirm] : ZBEUeactants) — ZBE(pr0ducts) BEEmzo .6 EmEtman 3552:: 23m 092.0 :30; Bow © To,va Eu E< :n- mu_oc:o< mm Qm r a we to? 3m Em 523:3 8 S h. HEB). ENE ENS mEm—z :02 mm .- "— mw hm www— m0 mm tymm an”. t.” owwm , mr mmNN F~Z : mEmEEm. 9: ho 22m... o=uo:wn_ ...
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chem200 f06 Beauvais exam3c - CHEM 200 Exam 3C November 29,...

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