Exam 3 2018 SDSU PDF

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Exam Midterm of Chem 200 SDSU...

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CHEM 200/202 Fall 2018

CHEM _______

Exam 3-A

November 17, 2018

Lab Section Number: _____

Name (printed):_____________________________________________ Signature:______________________________________ This exam consists of 36 questions all of equal value for a total of 225 points. Make sure that your test has all of the pages. Please read each problem carefully. There are no intentionally misleading questions; each problem should be taken at its face value. Please mark your answers on the Scantron sheet provided to you and on the actual exam. You will be given a periodic table and an exam information sheet to use during the exam. You may remove it from the exam make it more accessible. You may also use the designated Casio fx-300ms-plus calculator or equivalent non-programmable non-graphing scientific calculator during the exam. Use the back pages of the test as scratch paper. You are not allowed to use any devices capable of accessing the internet, textbooks, notes, or homemade reference sheets during the exam. You may leave if you finish the exam early. Give the exam and the information sheet to your TA and leave quietly without disturbing other students. Before leaving, check that all your answers have been properly entered on the Scantron sheet and the exam and that your name is written on every page of the exam and on the Scantron sheet. All cell phones and electronic devices must be turned off and put away. Please remove all hats and caps. Place your books and all papers out of sight under your seat. If the TA believes that you might be looking at your neighbor’s paper, you will be asked to move to a new location. Exam scores will be posted on Blackboard as soon as the grading is complete. Your test will be returned to you in the first lab meeting of next week. If you have any questions regarding the grading of your exam, please notify your TA. The time available for the exam is 120 minutes. Good luck!! 1  of 11

CHEM 200/202 Fall 2018

Exam 3-A

Name: ___________________________________________

November 17, 2018 Lab Section #: _______

Please mark your answers on the scantron sheet using a #2 pencil and also mark your answers on the exam itself. Mark Test From “A” on your scantron.

1. Which one of the following properties is least characteristic of substances composed of small, covalently-bonded molecules? (a) (b) (c) (d) (e)

brittle low boiling point poor electrical conductor when solid poor electrical conductor when molten high melting point

2. In which of these substances are the atoms held together by polar covalent bonding?" (a) (b) (c) (d) (e)

S8 SrCl2 CsCl CaF2 ClF"

3. Select the element whose Lewis dot structure is correct." (a) (b) (c) " (d) (e) 4. Which of the following contains ionic bonding? (a) (b) (c) (d) (e)

SrF2 CO2 H2O HF Al"

"

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5. Select the correct formula for a compound formed from barium and nitrogen. (a) (b) (c) (d) (e)

Ba3N2 Ba2N Ba2N3 BaN BaN2

6. Select the element with the lowest electronegativity." (a) (b) (c) (d) (e)

Li Al Cl Cs Ca"

7. Select the compound with the highest lattice energy." (a) (b) (c) (d) (e)

BaO NaI LiBr MgO CaS" "

8. Select the most polar bond amongst the following. (a) (b) (c) (d) (e)

C–O Si–F Cl–F C–F C–I

9. Select the correct Lewis structure for ClCN."

(a) (b) (c)" (d) (e)

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CHEM 200/202 Fall 2018

Exam 3-A

November 17, 2018

10. Oxygen difluoride is a powerful oxidizing and fluorinating agent. Select its Lewis structure." (a) (b) (c) (d) (e) None of the above are correct. 11. In which of the following is the best Lewis structure a resonance structure? (a) (b) (c) (d) (e)

SO3 BF3 I3– SCO (C is the central atom) SO32-"

12. The formal charge on Cl in the structure shown for the perchlorate ion is (a) -2 (b) +1 (c) 0 (d) -1 (e) +2 13. In which one of the following species is the central atom (the first atom in the formula) an exception to the octet rule? (a) (b) (c) (d) (e)

SF6 NH3 NH4+ I2 BH4– "

14. Considering all the bonds in a molecule with trigonal bipyramidal geometry, what are the bond angles present? (a) (b) (c) (d) (e)

120º only 90º only 90º, 120º, and 180º 60º and 90º only 180º only!

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15. What is the molecular shape of BCl3 as predicted by VSEPR theory? (a) (b) (c) (d) (e)

linear tetrahedral trigonal planar trigonal pyramidal none of the above

16. What is the molecular shape of NO2– as predicted by the VSEPR theory? (a) (b) (c) (d) (e)

bent tetrahedral T-shaped trigonal pyramidal linear

17. What is the molecular shape of XeO2F2 as predicted by the VSEPR theory?" (a) (b) (c) (d) (e)

square planar see-saw tetrahedral square pyramidal octahedral"

18. Which one of the following molecules and ions will have a square planar geometry as predicted by the VSEPR theory?" (a) (b) (c) (d) (e)

PCl3 BF4– XeF4 BrF5 H3O+"

19. In which of the molecules below does the central atom have an sp3d2 orbital hybridization?" (a) (b) (c) (d) (e)

XeF2 H2O CH4 XeF4 SO42–

20. What is the hybridization of the central atom in a molecule of NH3 ?" (a) (b) (c) (d) (e)

sp sp2 sp3 sp3d sp3d2

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CHEM 200/202 Fall 2018

Exam 3-A

November 17, 2018

21. What is the molecular structure and electron pair geometry of H2S? (a) (b) (c) (d) (e)

Trigonal bipyramidal and Linear Linear and Tetrahedral Bent and Tetrahedral Tetrahedral and Bent Linear and Linear

22. The electronic structure of the CO32- molecule is best represented as a resonance hybrid of ___ equivalent structures and what is the formal change of C?" (a) (b) (c) (d) (e)

2, +1 3, +2 4, +2 3, 0 This molecule does not exhibit resonance, +1

23. Estimate the heat of reaction at 298 K for the reaction shown, given the average bond energies below: 2H2(g) + O2(g) → 2H2O(g)

Bond Energy (kJ/mol)

(a) (b) (c) (d) (e)

H-H

O=O

H-O

436

499

463

1371 kJ -481 kJ 935 kJ -926 kJ -1353 kJ

24. The perchloric acid (HClO4) molecule contains? " (a) (b) (c) (d) (e)

13 lone pairs, 1 pi bond, and 4 sigma bonds. 9 lone pairs, no pi bonds, and 6 sigma bonds. 8 lone pairs, 2 pi bonds, and 7 sigma bonds 8 lone pairs, 3 pi bonds, and 5 sigma bonds. 11 lone pairs, no pi bonds, and 5 sigma bonds.

25. Which of the following molecules is non-polar ? (a) H2O (b) XeF4 (c) BrCl3 (d) CH3CH2OH (e) CH3Cl"

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CHEM 200/202 Fall 2018

Exam 3-A

November 17, 2018

To the right is a molecule of Ibuprofen. The lone pairs of electrons have been omitted for clarity. Every atoms in the structure follows the octet rule. Use the structure in answering the following 4 questions. 26. How many lone pairs of electrons are there on a molecule of Ibuprofen ? (a) 4 (b) 5 (c) 6 (d) 8 (e) 10" 27. How many of the carbon atoms in a Ibuprofen molecule have sp2 hybridization?" (a) (b) (c) (d) (e)

3 4 5 6 7"

28. How many pi (π) bonds are there on the molecule of Ibuprofen ?" (a) (b) (c) (d) (e)

2 4 6 8 10"

29. How many carbon atoms in the Ibuprofen structure adopts the sp3 hybridization?" (a) (b) (c) (d) (e)

2 3 4 5 6"

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CHEM 200/202 Fall 2018

Exam 3-A

November 17, 2018

Use the molecular orbital diagrams below to answer the following 4 questions.

 30. Which of the molecules listed below does not have a bond order of 2? (a) O2 (b) F22+ (c) ONe (d) C2 (e) CN+" 31. For the molecular N2+. The number of electrons in the σ 2p molecular orbital is" (a) (b) (c) (d) (e)

0 1 2 3 4"

32. What is the bond order for a molecule of O2+? (a) 0.5 (b) 1 (c) 1.5 (d) 2 (e) 2.5" 33. For the molecule B2, the number of unpaired electrons is _____" (a) (b) (c) (d) (e)

0 1 2 3 4

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November 17, 2018

34. According to the valence bond theory, which is the best definition of a pi (π) bond?" (a) A removal and transfer of electrons from one atom to another. (b) A side-by-side overlap of two p orbitals. (c) The out-of-phase overlap of atomic orbitals, resulting in a node along the internuclear axis. (d) The presence of two orbitals with the same energy near their respective nuclei. (e) A covalent bond formed by the overlap of atomic orbitals along the internuclear axis. 35. Antibonding molecular orbitals are produced by (a) constructive interaction of atomic orbitals. (b) destructive interaction of atomic orbitals. (c) the overlap of the atomic orbitals of two negative ions (d) all of these (e) none of these 36. When a double bond is formed between two carbon atoms in the ethylene (C2H4) molecule, one of the bond is a sigma bond and the other is a pi bond, the sigma bond is formed by overlap of __? (a) P orbitals (b) S orbitals (c) sp hybrid orbitals (d) sp2 hybrid orbitals (e) sp3 hybrid orbitals

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