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Chemistry 301 Exam 2 - Barkley Thane Exam 2 Due 11:00 pm...

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Barkley, Thane – Exam 2 – Due: Oct 18 2007, 11:00 pm – Inst: McCord 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. McCord 11 AM ONLY ! ! ! ! 001 (part 1 of 1) 10 points Which molecule would you predict would be more stable: O 2 - 2 or O 2+ 2 ? 1. O 2 - 2 2. O 2+ 2 correct 3. They would be equally stable. Explanation: 002 (part 1 of 1) 10 points How many σ and how many π bonds are there in HCN? C is the central atom. 1. 2; 2 correct 2. 1; 1 3. 3; 1 4. 4; 4 5. 4; 0 Explanation: The structure of HCN is C · · N H C is triple bonded to N and single bonded to H. There is one single ( σ ) bond and one triple double ( π + σ + π ) bond. Thus, there are two σ bonds and two π bonds. 003 (part 1 of 1) 10 points How many dots should appear in the Lewis electron structure for the silicon atom? 1. 8 2. 4 correct 3. 6 4. 2 Explanation: Silicon is in group IVB, right below car- bon. Just like all the other elements in the group IVB, silicon has 4 electrons in its out- ermost shell. These outermost electrons (the so-called “valence electrons”) are represented by dots in a Lewis dot formula. 004 (part 1 of 1) 10 points Arrange the compounds BaO , SiO 2 , SO 2 in order of increasing ionic character (most ionic at the right). 1. BaO, SiO 2 , SO 2 2. SO 2 , BaO, SiO 2 3. SiO 2 , SO 2 , BaO 4. BaO, SO 2 , SiO 2 5. SO 2 , SiO 2 , BaO correct Explanation: As the metallic character of the element bonded to oxygen increases, the ionic charac- ter of the bond increases. In general, metallic character increases from top to bottom and from right to left in the Periodic Table. 005 (part 1 of 1) 10 points Which of the following has the highest lattice energy? 1. BaO 2. NaCl 3. KI 4. MgO correct
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Barkley, Thane – Exam 2 – Due: Oct 18 2007, 11:00 pm – Inst: McCord 2 5. CaO Explanation: Mg 2+ and O 2 - have the highest charge den- sities. 006 (part 1 of 1) 10 points Which of the following has only one π bond? 1. HCl 2. H 2 O 3. N 2 4. H 2 CO correct 5. Cl 2 6. H 2 C 2 Explanation: 007 (part 1 of 1) 10 points The bond angle in NH 3 is (smaller, larger) than the bond angle in CH 4 because 1. smaller; the unshared pair of electrons on nitrogen is more repulsive to the bonded electron pairs. correct 2. larger; the hybridization of nitrogen re- sults in larger bond angles than the hybridiza- tion of carbon.
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