PracticeExamII_Solutions Test 2

PracticeExamII_Solutions Test 2 - Livasy David Exam 2 Due...

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Livasy, David – Exam 2 – Due: Oct 6 2006, 4:00 pm – Inst: Donna C Lyon 1 This print-out should have 21 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points Which of the following is the best represen- tation of the compound potassium sulfide? 1. 3 K 2+ , 2 S 3 - 2. None is appropriate because potassium sulfide is a covalent compound. 3. 2 K + , S 2 - correct 4. K + , S - 5. K 2+ , S 2 - 6. K 2+ , 2 S - Explanation: 002 (part 1 of 1) 10 points Which of the following statements about po- larity is false? 1. Dipole moments can “cancel”, giving a net non-polar molecule. 2. Lone (unshared) pairs of electrons on the central atom play an important role in influ- encing polarity. 3. Linear molecules can be polar. 4. CCl 4 is a polar molecule. correct 5. Polar molecules must have a net dipole moment. Explanation: The Lewis Dot structure for CCl 4 is C · · · · ·· Cl · · · · ·· Cl · · · · · · Cl · · · · ·· Cl The molecule has tetrahedral electronic and molecular geometry. The C - Cl bond is polar, but becuase of the symmetry of the molecule, the individual dipole moments cancel. The molecule is therefore nonpolar. 003 (part 1 of 1) 10 points This is a case in which P desires to be sur- rounded by ten electrons. The polyatomic ion PCl - 4 has ? electronic arrangement and ? molecular shape. 1. octahedral; square planar 2. trigonal bypyramidal; tetrahedral 3. trigonal bipyramidal; T-shaped 4. tetrahedral; trigonal pyramidal 5. trigonal bipyramidal; seesaw correct 6. tetrahedral; tetrahedral Explanation: Because P desires 10 electrons, this means there are 5 regions of HED. This corresponds to trigonal bipyramidal electronic geometry. Eight of the ten electrons are bonding elec- trons. The other two electrons are a lone pair which gives seesaw molecular geometry. 004 (part 1 of 1) 10 points Given that elements Na and Cl are bonded and the electronegativity difference is 2.1, de- termine the bond type and the more-negative atom. 1. None of these 2. polar-covalent bond; Na 3. ionic bond; Cl correct
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Livasy, David – Exam 2 – Due: Oct 6 2006, 4:00 pm – Inst: Donna C Lyon 2 4. ionic bond; Na 5. nonpolar-covalent bond; same electroneg- ativity 6. ionic bond; same electronegativity 7. nonpolar-covalent bond; Na 8. polar-covalent bond; same electronegativ- ity 9. polar-covalent bond; Cl 10. nonpolar-covalent bond; Cl Explanation: Electronegativity difference = 2.1
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