EXAM2 - Version 285 Exam 2 mccord (50970) 1 This print-out...

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Unformatted text preview: Version 285 Exam 2 mccord (50970) 1 This print-out should have 34 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. McCord CH301 001 10.0 points Which of the following symbols is used to depict a partial positive charge? 1. + 2. + correct 3. + 4. + 5. + 6. + Explanation: 002 10.0 points Which of the following molecules is non- polar? 1. H 2 O 2. O 3 3. PH 3 4. H 2 O 2 5. XeF 4 correct Explanation: XeF 4 is symmetrical and therefore non- polar. Ozone (O 3 ) is the only polar molecule composed of non-polar bonds. The other molecules are all asymmetrical and therefore polar. 003 10.0 points More than one Lewis formula resonance struc- ture can be drawn for which of the following for minimum formal charge? 1. H 2 O 2. SbH 3 3. O 3 correct 4. CO 2 5. SF 4 Explanation: Oxygen is double bonded to one of the oxy- gen atoms and singly bonded to the third oxygen atom. The double bond can shift from one of the positions to the other to give rise to resonance structures. 004 10.0 points In the Lewis dot structure of the molecule ClF 3 , how many unbonded electron pairs are found around the central atom? 1. 2 correct 2. 1 3. 4. 3 5. 4 Explanation: Draw the Lewis dot structure. ClF 3 has 3 Cl F single bonds and 2 lone pairs on Cl. 005 10.0 points The lattice enthalpy of calcium oxide is the energy change for the reaction 1. CaO(s) Ca 2+ (g) + O 2 (g) correct 2. Ca(s) + 1 2 O 2 (g) CaO(s) 3. CaO(s) Ca(g) + 1 2 O 2 (g) 4. Ca(g) + O(g) CaO(g) 5. CaO(s) Ca(g) + O(g) Version 285 Exam 2 mccord (50970) 2 Explanation: Lattice enthalpy is the energy change at constant pressure when a 1 mole of an ionic solid is broken into ions of its component elements in gaseous form at 298 K, 1 atm. 006 10.0 points What is the electronic geometry around ni- trogen in the molecule CH 3 CH 2 NH 2 ? 1. linear 2. tetrahedral correct 3. trigonal pyramidal 4. square planar 5. bent 6. trigonal planar Explanation: 007 10.0 points What hybridization would you expect for the carbon atoms in the cyclic compound benzene (C 6 H 6 )? 1. sp 3 d 2 2. sp 3. sp 3 d 4. sp 3 5. sp 2 correct Explanation: In each carbon one s orbital and two p or- bitals hybridize to produce three sp 2 orbitals which form sigma bonds between the carbons and between carbon and hydrogen. The re- maining p orbitals form pi bonds between the carbons. 008 10.0 points How many and bonds are in the molecule below? C C H N b b H H 1. 5 , 2 correct 2. 7 , 1 3. 6 , 2 4. 6 , 1 5. 5 , 1 Explanation: Sigma bonds are the first bond formed be- tween any two bonded atoms. Any subse- quent bond is a pi bond....
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EXAM2 - Version 285 Exam 2 mccord (50970) 1 This print-out...

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