Exam 2 T Th-solutions - Version 184 Exam 2 T Th sutcliffe...

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Unformatted text preview: Version 184 Exam 2 T Th sutcliffe (50985) 1 This print-out should have 35 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points How many double bonds are in the compound CH 2 CHCH 2 CHCH 2 ? 1. 1 2. 2 correct 3. 3 4. 4 5. Explanation: The Lewis dot structure is H C H C H C H H C H C H H 002 10.0 points SO 2 4 is more/less polar than SO 2 3 because 1. less; the four polar S O bonds in SO 2 4 are symmetrical and cancel the dipole moments. correct 2. less; it is a resonance structure. 3. more; the tetrahedral geometry increases the polarity of S O bonds 4. more; it has four polar S O bonds rather than three polar S O bonds. 5. more; the four polar S O bonds in SO 2 4 are arranged non-symmetrically leaving a net dipole moment. Explanation: SO 2 4 has no lone pairs on the central S atom. It has tetrahedral molecular geometry. Each bond angle is 109.5 . The dipole mo- ments cancel and the molecule is non-polar. SO 2 3 has one lone pair on the central S atom. It has pyramidal molecular geometry. The bond angles are not equal so the dipole moments cannot cancel. This molecule is polar. 003 10.0 points Predict the N O bond lengths in NO 2 , given the N O and N O bond lengths of 140 and 120 pm, respectively. 1. both 140 pm 2. both 120 pm 3. both 130 pm correct 4. None of these 5. single bond: 140 pm; double bond: 120 pm Explanation: N b b O b b b b b b O b b b b N b b O b b b b b b O b b b b B.O. = 1.5 004 10.0 points Acetylene (HCCH) is a linear molecule. 1. False 2. True correct Explanation: H C C- H 005 10.0 points Draw the Lewis structure for the molecule containing two H and one Se atoms. How many single bonds, double bonds, triple bonds, and unshared pairs of electrons are on the central atom, in that order? 1. 0, 0, 1, 1 2. None of these Version 184 Exam 2 T Th sutcliffe (50985) 2 3. 4, 0, 0, 0 4. 0, 1, 1, 0 5. 3, 0, 0, 1 6. 2, 0, 0, 2 correct 7. 1, 0, 1, 0 8. 2, 1, 0, 0 9. 0, 2, 0, 0 10. 1, 1, 0, 1 Explanation: Se has 6 valence electrons; H has one va- lence electron: b b b b b b Se b H Total number of valence electrons: Se 1 6 e = 6 e H 2 1 e = 2 e 8 e Thus the Lewis dot structure is b b b b b b b b H Se H and the central atom has 2 single bonds and two unshared electron pairs. 006 10.0 points Be sure to make sure you minimize formal charge in your structure. How many electrons are around the central atom in the expanded valence in XeO 4 ? 1. 18 2. 16 correct 3. 12 4. 10 5. 20 Explanation: All atoms have a formal charge of zero in the most plausible structure: Xe O b b b b O b b b b O b b b b O b b b b 007 10.0 points Which of the following contains both covalent and ionic bonding?...
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Exam 2 T Th-solutions - Version 184 Exam 2 T Th sutcliffe...

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