chem exam2laude - Warsi, Kusum Exam 2 Due: Nov 7 2006, 4:00...

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Unformatted text preview: Warsi, Kusum Exam 2 Due: Nov 7 2006, 4:00 pm Inst: David Laude 1 This print-out should have 30 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. The due time is Central time. You may only use your calculators, periodic table, formula sheet and scratch paper for this test. You will have the full period to take this exam. DO NOT FORGET YOUR VERSION NUMBER! Good luck! 001 (part 1 of 1) 6 points How many valence electrons does N + 2 have and what is its bond order? 1. None of these 2. 6; 1 3. 14; 1 4. 10; 3 5. 9; 2.5 correct 6. 4; 0 7. 9; 1 Explanation: N + 2 : ( 2 s ) 2 ( * 2 s ) 2 ( 2 p x ) 2 ( 2 p y ) 2 ( 2 p ) 1 has 9 valence electrons and a bond order of 2.5. 002 (part 1 of 1) 6 points Which of the following, in the solid state, would be an example of a molecular crystal? 1. None of these 2. diamond 3. iron 4. barium fluoride 5. carbon dioxide correct Explanation: CO 2 is a covalent molecule. Any extended lattice among covalent molecules will be held together by intermolecular forces: H-bonds, London forces, and dipole-dipole interactions. Covalent bonds are not found between CO 2 molecules, only within the molecule; there- fore, the crystal will be molecular. 003 (part 1 of 1) 6 points Which of the following substances has a delo- calized bond? 1. CO 2. ClO- 3 3. CO 2 4. NH 3 5. CO 2- 3 correct Explanation: Delocalized bonds occur whenever reso- nance occurs. In a molecule that exhibits resonance, the bond has partial double and partial single bond character. This means that electrons are delocalized around the res- onance bond. CO 2- 3 is the only compound that exhibits resonance and therefore delocal- ization. 004 (part 1 of 1) 6 points A 6.35 L sample of carbon monoxide is col- lected at 55 C and 0.892 atm. What volume will the gas occupy at 1.05 atm and 59. C? 1. 6.68 L 2. 5.46 L correct 3. 1.96 L 4. 6.10 L 5. 4.82 L Explanation: V 1 = 6 . 35 L P 1 = 0 . 892 atm T 1 = 55 C = 328 K P 2 = 1 . 05 atm T 2 = 59 C = 332 K We can use the combined gas law and solve Warsi, Kusum Exam 2 Due: Nov 7 2006, 4:00 pm Inst: David Laude 2 for V 2 : P 1 V 1 T 1 = P 2 V 2 T 2 V 2 = P 1 V 1 T 2 T 1 P 2 = (6 . 35 L)(0 . 892 atm)(332 K) (328 K)(1 . 05 atm) = 5 . 46 L 005 (part 1 of 1) 6 points What is the density of carbon tetrachloride vapor at 714 torr and 125 C? 1. 6 . 62422 g / L 2. 2 . 9441 g / L 3. 4 . 41615 g / L correct 4. 5 . 52018 g / L 5. 3 . 53292 g / L Explanation: T = 124 + 273 = 397 K P = 710 torr atm 760 torr = 0 . 934211 atm n V = ? P V = nR T n V = P R T = (0 . 934211 atm) (0 . 08206 L atm mol K )(397 K) = 0 . 0286763 mol L . 0286763 mol L 154 g mol = 4 . 41615 g / L 006 (part 1 of 1) 6 points The smallest bond angles would be found in the compound with the following molecular geometry: 1. square planar correct 2. angular 3. trigonal bipyramidal 4. trigonal planar 5. linear Explanation: 007 (part 1 of 1) 6 points...
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This note was uploaded on 02/25/2010 for the course CH 54363 taught by Professor Mccord during the Spring '08 term at University of Texas at Austin.

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chem exam2laude - Warsi, Kusum Exam 2 Due: Nov 7 2006, 4:00...

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