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Exam-2 - Rahman Tarique Exam 2 Due 11:00 pm Inst Vandenbout...

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Rahman, Tarique – Exam 2 – Due: Oct 18 2007, 11:00 pm – Inst: Vandenbout 1 This print-out should have 27 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. VandenBout 2 PM ONLY ! ! 001 (part 1 of 2) 10 points What is the structure of CF 3 Cl? 1. octahedral 2. square pyramidal 3. trigonal planar 4. tetrahedral correct 5. trigonal pyramidal 6. seesaw Explanation: C F F F Cl is tetrahedral (AX 4 ). 002 (part 2 of 2) 10 points Predict the bond angles. 1. 90 and 180 only 2. 90 and 120 only 3. 120 only 4. 109 . 5 only correct 5. 120 , 90 , and 180 6. 80 Explanation: All halogen - C - halogen bond angles should be approximately 109.5 . 003 (part 1 of 1) 10 points Which of the following has the highest lattice energy? 1. NaCl 2. BaO 3. CaO 4. MgO correct 5. KI Explanation: Mg 2+ and O 2 - have the highest charge den- sities. 004 (part 1 of 1) 10 points Consider CN + , CN and CN - . Based on a molecular orbital diagram, which of these will have the shortest bond length? 1. CN 2. CN and CN - are both the same and shorter than CN + . 3. CN + 4. CN - correct 5. The bond lengths are all the same. Explanation: The bond order is # bonding e - - # antibonding e - 2 The bond orders of the species are CN - BO = 10 - 4 2 = 3 CN BO = 9 - 4 2 = 2 . 5 CN + BO = 8 - 4 2 = 2 The higher the bond order, the shorter the bond length.
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Rahman, Tarique – Exam 2 – Due: Oct 18 2007, 11:00 pm – Inst: Vandenbout 2 005 (part 1 of 1) 10 points Which molecule would you predict would be more stable: O 2 - 2 or O 2+ 2 ? 1. They would be equally stable. 2. O 2+ 2 correct 3. O 2 - 2 Explanation: 006 (part 1 of 1) 10 points The Lewis dot structure of CO 2 - 3 has how many total electrons and how many shared electrons? 1. 32; 6 2. 24; 6 3. 24; 10 4. 32; 8 5. 32; 10 6. 24; 8 correct Explanation: The total number of valence electrons is 1 × 4 e - (for C) + 3 × 6 e - (for O) +2 e - (from - 2 charge) = 24 e - C is the central atom, with the O atoms arranged around it. C will have an incomplete octet if we show one shared pair of electrons (a single bond) with each O, so one double bond is necessary: C O O O 007 (part 1 of 1) 10 points The chemistry of an element is largely deter- mined by 1. its relative abundance. 2. its valence electrons. correct 3. its mass. 4. its core electrons. 5. its number of total electrons.
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