Exam 3 Sample Problems - Possible questions S08 CHEM 151 Do...

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Possible questions S08 CHEM 151 Do simple oxidation numbers from Lewis structures. (2) According to VSEPR theory, a molecule with the general formula AX 2 E 2 will have a _____ structure (a) linear (b) pyramid (c) tetrahedral (d) bent (e) twisted 1. (2) Which molecule violates the octet rule? (a) BF 4 - (b) NF 4 + (c) NO 3 - (d) NO 2 (e) NO 2 + 2. (2) Electronegativity is (a) The energy released when an atom picks up an electron. (b) The energy needed to remove the loosest electron from an atom. (c) The maximum positive charge the atom can acquire. (d) The maximum negative charge an atom can acquire. (e) The power of an atom in a molecule to attract electrons to itself. 3. (2) In the molecule below, the <HCC angle is C C C H H H F F F (a) 60 degrees (b) 90 degrees (c) 109.5 degrees (d) 120 degrees (e) 180 degrees 4. (2) Which molecule is not polar ? (a) CO (b) SO 2 (c) SO 3 (d) SO (e) NO 5 6. (2) This question deals with the bond angles in dinitrogen tetroxide. The Lewis structure is shown below. What is the NNO angle? N N O O O O (a) 60 o (b) 90 o (c) 109.5 o (d) 120 o (e) 180 o
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4) What is the MOLECULAR GEOMETRY ( SHAPE ) for PH 3 ? A) square planar B) trigonal . bipyramid C) trigonal . pyramid D) tetrahedron E) trigonal . planar 5) For a transition metal Fe 2+ ion the configuration [Ar]4s 0 3d 6 is an : A) excited state-- Should be [Ar]4s 2 3d 4 B) ground state of normal ion C) impossible D) I got it wrong before so I’ll be wrong again. 7) Which of the following covalent BONDS is least polar? (this is not a trick question) Pauling Electronegativities F = 4.0 P = 2.1 Cl= 3.0 H = 2.1 A) F―Cl B) Cl―P C) P―H D) F―H Cl―H 8) Water is critical to life on earth and has many unusual properties (solid floats on liquid, exceedingly high boiling point, etc.). Many of these are related to: A) Ionic forces between charged molecules B) Macromolecular combinations increase bonding C) Vander waals (dispersion) forces between polar bonds D) Hydrogen bonding E) Ordinary dipole-dipole forces 9) A material is hard, crystalline, not conducting at room temperature, but conducts electricity when melted. It probably is: A) ionic B) covalent C) metallic D) can’t determine 10) Which of the following general classes of organic compounds could form hydrogen bonds with itself? ( hint : draw out the structures) I organic acids -COOH II amines -C-NH 2 III ethers -C-O-C A) I and II B) III only C) I only D) II and III E) I and III ________________________________________________________________________________ 11) (6 points) Including where appropriate electron pairs; brackets; double headed arrows and charges draw all the best resonance structures for CO 3 2-
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13)(15pts) Based on their geometry and bond polarity identify each of the following molecules as POLAR or NON-POLAR: You MUST draw the structures and SHOW the arrows separately for the polar bonds used to reach your conclusions. Show in your drawing or in words how the arrows add or cancel. Pauling Electronegativites
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This note was uploaded on 06/12/2008 for the course CHEM 151 taught by Professor Staff during the Spring '08 term at University of Arizona- Tucson.

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Exam 3 Sample Problems - Possible questions S08 CHEM 151 Do...

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