Exam2 - Pickering Tracey – Exam 2 – Due 3:00 pm – Inst McCord 1 This print-out should have 20 questions Multiple-choice questions may

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Unformatted text preview: Pickering, Tracey – Exam 2 – Due: Oct 19 2005, 3:00 pm – Inst: McCord 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. Results will be available around 3 PM to- day. Ozone: O 3 001 (part 1 of 1) 10 points Which of the following angles is the best de- scription of the O-O-O bond angle in O 3 (ozone)? 1. 180 ◦ 2. 90 ◦ 3. 117 ◦ correct 4. 122 ◦ 5. 109.5 ◦ 6. 107 ◦ 7. 120 ◦ Explanation: Ozone has 3 electron regions around the central oxygen (double bond, single bond, and a lone pair). This gives a trigonal planar electronic geometry from which to build. The bond angle starts out at 120 ◦ as any trigonal planar geometry would. HOWEVER! The lone pair electrons are MORE repulsive than the bonding pairs and therefore distorts the trigonal planar shape. The bond angle is squeezed slighly to a bond angle of 117 ◦ which is the BEST answer. 002 (part 1 of 1) 10 points How many lone pairs of electrons are found in the Lewis structure of urea ((NH 2 ) 2 CO)? 1. 3 2. 2 3. 4 correct 4. 6 5. 8 Explanation: The Lewis structure is C O H 2 N NH 2 003 (part 1 of 1) 10 points Which of the following is a polar molecule? 1. XeF 2 2. SF 6 3. CO 2 4. CH 4 5. SO 2 correct Explanation: SO 2 has 1 lone pair on S and two S O bonds. The best structure for formal charge has both bond as double bond. This leaves all three atoms with zero for for- mal charge. The electronic geometry is trig- onal planar with one lone pair of electrons. This will cause the molecule to be polar. 004 (part 1 of 1) 10 points How many non-bonding electron pairs are around I in IF- 2 ?...
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This note was uploaded on 06/23/2008 for the course CH 301 taught by Professor Fakhreddine/lyon during the Fall '07 term at University of Texas at Austin.

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Exam2 - Pickering Tracey – Exam 2 – Due 3:00 pm – Inst McCord 1 This print-out should have 20 questions Multiple-choice questions may

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