cem181f06e2a - Chemistry 181H Fall, 2006 EXAM II Thursday,...

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Unformatted text preview: Chemistry 181H Fall, 2006 EXAM II Thursday, 9 Nov 2006 WRITE your Name' W Student Number Recitation Time: Monday There are 5 questions on this exam, worth 20 points each. Write your answer, showing all work to each on each page. A list of potentially useful equations is on page 7. A periodic table is contained on page 9. # Score 1 / 20 2 / 20 3 / 20 4 / 20 5 / 20 1. Answer the following questions about the ozone molecule, 03. (a) (4 points) Draw the two Lewis resonance structures for ozone. 9241;) AL W Elm,er , 0° 'fi’fi'w:d%& .0 ’ . 99 (b) (6 points) Redraw one of your Lewis structures in the space be— low and indicate the formal charge on each of the three oxygen isotopes. "aw" “- = 4" 2" #6) O FC=%-‘Io // \.d../;c=_1 adv—m) 4" "'i‘” (c) (5 points) What is the electron arrangement on the central oxygen atom and what is the 0-0—0 bond angle in ozone according to the VSEPR theory? (d) (5 points) What is the electron arrangement on the central phos— phorous atom and what is the O—P-O bond angle in the related molecule phosphorous dioxide according to the VSEPR theory? '1') '- 9904*“ ' O ' o alwfi— *0 ‘30. .9 O .- 2. Consider the two related molecules, dichloroethylene (C2HQClg) and dichloroethyne (C2012). (a) (4 points) Draw the Lewis structure of dichloroethyne (C2012) and indicate the value of either Cl—C-C bond angle using the VSEPR theory. '80 o :éQI/c-Zc— (b) (6 points) Describe in words all of the bonds between the two carbon atoms in dichloroethyne, 02012, using the Valence Bond theory. Be sure to indicate any hybridization on the carbon atoms if present. ‘AP (IT-150M" - Z‘P" {2(17 an “99.. (c) (6 points) Draw the Lewis structure for each of the three dichloroethylene, 021—12012, molecules and indicate the value of either Cl—C-C bond an 1e in each molecule. H g a H \ l H 4.4 Q \ .. C. = C. \ a /°‘»:,< a u.’ 'Ur 0L a; J ‘H tabs . lZo° £20" WM) all 120.1 (d) (4 points) Describe in words the bonds between the two carbon atoms in dichloroethylene, CzHgClg, using the Valence Bond the— ory. Be sure to indicate any hybridization on the carbon atoms if present. EMMA - A?2 W4. W FM " we 21: mmaqé'mlrw {oum’lt'éaé 3 3. Consider the neutral molecular fragment nitrogen monohydride, NH. (a) (5 points) Write the valence bond wavefunction, \IIVB , for the NH bond. Be sure to include the electron spins. V n 1’ b: «luzgl (q’Hl/J‘b +- ll,” \l’ql’Hl/f (b) (5 points) Draw the LCAO molecular orbital energy level diagram for the NH molecule. For reference the PIP of hydrogen is 13.6 eV and of nitrogen is 14.5 eV. Be sure to indicate the positions of the atomic and molecular orbitals. (c) (5 points) Do you expect the NH bond to be polarized or unpo- larized? Give a concise reason for your answer. Palu’ ¢L .. we Aokhoe MJMWCM axial; w . gT'WJI-ch not): emwmwbfi Mlheww' 7407-? a»; N Ho wibl awe a. CAAYA (d) (5 points) Do you expect this fragment to be diamagnetic or para- magnetic? Give a concise reason for your answer. panamawic— , ‘l'wv MM— wolr- mercuwiz A0. 4 4. Calculate the bond order from the LCAO-MO theory for each of the following to decide if the addition of an electron to each of the following molecules makes the ion more or less stable than the molecule. (5 points each pair: 2 for each bond order, 1 for comparison) (a) Li2 is@or less stable than Ll2_ .. 3e- zocoQ— tbo; 1 ?B.o. = 12- (b) N2 is or less stable than N2_ N) -— ‘16.— M f B. 0;: 7> {1&0 ‘1 572, (c) BC is more ortable than BC“ ’5 - 2" a " b E. 9.0. = 0; z (d) OP is or less stable than or 0 ._ 5 e- F - 7e - {5.0; 3; (6:0; 1 5. The ethylene molecule, C2H4, has a double bond with a 0—0 bond length of approximately 130 pm. Estimate the energy of the photon that would be absorbed in the 7r —> 7r* transition in this molecule. <‘* m rm; 4..» m 2? Renewab- H ~W1‘3“\WM%TMMWW3WJ’€Q A)? ‘l‘toa Jaw-€343 LL26$lt§3413Z :: (M 2" 2 (22- 3| 3? ‘- 63le 8(1th “3303” _|& AF: ; [44) 5445‘” T .i?/ A5 g: l0? Nb J ...
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This note was uploaded on 07/25/2008 for the course CEM 181h taught by Professor Morrissey during the Fall '08 term at Michigan State University.

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cem181f06e2a - Chemistry 181H Fall, 2006 EXAM II Thursday,...

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