Chem 105 Exam 3 and Key (Fall 2007)

Chem 105 Exam 3 and Key (Fall 2007) - Chemistry 105' 7 Exam...

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Unformatted text preview: Chemistry 105' 7 Exam 3 Nov. ‘15, 2007 I 'SW/NW ‘ Form 2 Page 1 Name: ID# - TA ‘ _ Lab Sec 1. The effective nuclear charge (2*) of an electron in the 2s orbital of carbon is 3.22, while that of an electron in a 2p Orbital is 3.14. Which of the following statements is/are true? ' i. These values of 2* are consistent with the 2p orbital being at a higher energy than the 23 orbital. ' 7 ii. The electrons in the 25 orbital screen the 2p electrons more than the 2p electrons screen the 25 electron. _ h iii. Electrons with nnl screen electrons from n=2 more completely than electrons in n=2 screen each other. Only i Only iii i and ii - All are true ii and iii econ? 2. What is the complete electron configuration of S? 152 2s2 2p6 2d6 132 1p6 252 2136 ls2 2s2 21:5 352 3p4 ls2 1p6 232 2p6 2d10 332 3p4 ls2 2s2 2336 352 3p6 3d10 4s2 4p2 WPOP‘? 3. Which of the following is the correct electron box diagram for V? _ A-[AflL filifim_ 4s_ 3d -B.[AI]E LLL__ _ 4s 3d 0. [Ar]_ LLLLI. r , 4s 3d D-[Arlfi Iii..___ 4s 3d EMflL lJ;L1__ 4s 3d 4. Place the following in order from the smallest to the largest based on the atomic radius: N, O, P A.O<P<N B.P<N<O C.N<P<O D.0<N<P E.N<O<P Form 2 Page 2 Chemistry 105 Exam _3 Nov. 15, 2007 - SWINW 5. Place the following in order from the smallest to the largest based on the first ionization energy: Br, C1, Se 7 ‘ Se<Br<C1 C1<Se<Br Se<Cl<Br Cl<Br<Se Br€Se<Cl some? 6. Match the value. of the electron affinity (kl/moi) with the element. ' Be F A. 328 0 B. -328 0 C. 328 -328 D. 0 -328 E. 0 +328 ' 7. For an atom of a main group element, the number of valence electrons is equal to . A. its number of core electrons. B. eight minus its group number. C. the principle quantum number of its outer shell. D. its group number. E. its period number. ' 8. Which of the following statements is/are CORRECT? i. Ionic bonds form when one or more valence electrons are transferred from one atom to another. ii. Covalent bonds involve sharing of electrons between atoms. iii. Ionic bond formation is always exothermic; covalent bond formation is always - endothermic. . iii only i only i, ii, and iii ii only -i ii wuow> Chemistry 105 Exam 3 Nov. 15,2007 SW/NW. Form 2 Page 3 9. Calculate the lattice energy of NaBr(s), given the following thermochemical equations. Na(s) —> Na(g) 7 AHf = 107 kJ Na(g) —> Na+(g) + e“ I ME =496 kJ - l/2 Br2(g) ——> Br(g) AH}? = 112 kJ Br(g) + e' -> Br‘(g) AEA = -325 kJ Na(s) + 1/2 Br2(g) '-+ NaBr(s) AHf" = -361 kJ +290 kJ +1,403 k} -963 Id -751 k] -290 kJ econ? 10. What is the total number of valence electrons in the C032” ion? 20 26 30 22 24 mace? 11. How many lone-pair electrons are on the carbon atom in C02? 3 wane? Now—hm Form 2 Page 4 ' -_ Chemistry 105 _ Exam 3 Nov. 15,2007 swmw 12. Which of the following is a correct Lewis structure for the phosphate ion (PO43; with P as the central atom). ; . - I - I... 3- - A... 3" '1'. 3— .T¢ .(I). ‘ Owl-[:02 10:13:03 IR: 191 :9: l 2 3 .. 3- .. 3— 3C!) ‘:o: IO Ell—‘0'. 353,! :0: 4 5 AA. 3 B. 4 C. 5 D. 1 E. 2 13. Which of the following are resonance structures for sulfur dioxide, 802? (I) (2) ' (3) . (4) A. 1, 2, and 3 B. 2, 3, and 4 C. 1 and 2 t D. 2 and 4 E. 3 and 4 14. Which of the following elements is most likely to form a molecular structure that disobeys the octet rule? ‘ A. N ween WOWO Chemistry :105 - Exam 3 7 Nov. 15,- 2007 SWINW Form '2 Page 5 15. Use VSEPR theoryto predict the molecular geometry of C032". trigonal-planar bent , T—shaped tetrahedral trigonalupyramidal 3015093? 16. What is the formal charge on each atom in a hypobromite ion, OBI“? A. Ox—1,Br=+l B. O=-2,Br=+l C. 020,Br=- D. O=—2,Br=- E. O=-1,Br=0 17. The standard molar enthalpy of formation of CIF3 is -405 kJ. I 1/2 C12(g) + 3/2 F2(g) —> C1F3(g) The bond energies of C12 and F2 are 242 id and 155 kJ/mol, respectively. Calculate the energy I of a Cl-lf‘lbond. I A. 8 kJ/mol B. 802 kJ/mol C. 207 kJ/mol D. 87 kJ/mol E. 253 kJ/mol 18. Which one of the following molecules has a dipole moment? A. C14 B. 303 C. 02 D. NC13 E. (:02 19. Whatis the hybridization of the S in the trigonal planar molecule SO3 (S is the central atom)? dsp3 Sp2 51) mace? d23p3 Form 2 Page 6 Chemistry 105 Exam 3 Nov. 15, 2007 SW/NW 20. Describe the type of bonds, 0 and/or it, between the two underlined carbon atoms in the foliowing molecule: H H—ng—“CWH \ H Three 0' bonds One TC bond and two 0 bonds Two at bonds and one 0 bond One at bond and one 0' bond Three TE bonds WUQW? ' 21. What is the hybridization of the N atom in NH4+? The ion is tetrahedral N at the center. when? CL a}? "U 03 22. Describe the bonding between the two underlined C atoms in the following molecule, indicating the type of bond and the hybrid on each atom contributing to the bond.. HH 1/ C—"H “\029/ H/— \C/” H A. A or bond involving an Sp2 hybrid on each C Another 6 bond involving an unhybridized p orbital on each C B. A 6 bond involving an Sp2 hybrid on each C Another 0‘ bond involving an unhybridized p orbital on each C C. Two 6 bonds, each of which uses an sp2 hybrid orbital on each C D. A 6 bond involving an sp2 hybrid on each' C A TE bond involving an unhybridized p orbital on each C E, A 71'. bond involving an $132 hybrid on each C I a 6 bond involving an unhybridized p orbital on each C 23. Consider the following molecules. Which, if any, will show restricted rotation about a bond, and thus another isomer of the molecule? H Br 7 H 3.- H H \_/ * \ a \ / C---C Hun—c H Hhc—O . / \ , I < I CI H c; H H i ii 111 A. Onlyii B. Onlyi C. All D. ii andiii E. iandii 24, Choose the one with the largest radius fiom each of the following pairs. Cs or Cs+ Cu2+ or Cu+ 0 or 02- , A. CS - Cu+ 02‘ B. CS ' Cu+ O C. Cs+ Cu2+ 02‘ D. Cs Cu+ O E, (38+ Cu2+ O 25. The amount of solvent (water) used for a reaction is sometimes significant to the calculations and sometimes immaterial. Consider the calorimetry experiment and the measurement of the heat of solution of NH4C1. i. For a particular amount, for example 2.5 g, of NH4C1, will the volume of water used affect the temperature change measured? Yes or No ii. Will the amount of water, so long as it is precisely known, affect the calculated heat of solution? Yes or No i ‘ ii A. Yes No - B. Insufficient information is provided. C. Yes Yes D. No Yes E. No No ' em 105 Exam 3 Key Fall 2007 wwwmmm: . pg ,2 magic: . ~ :1": mum: fl mfiwm '“r gag? ' " 3 2" mm mm 5: a”? Em“ 0:25.. a k (mm: imam 2%”: ° _, . 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Chem 105 Exam 3 and Key (Fall 2007) - Chemistry 105' 7 Exam...

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