CHEM 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 9
Name: 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 B on your scantron. 1. Which one of the following properties is least characteristic of substances composed of small, covalently-bonded molecules? (a) brittle (b) low boiling point (c) poor electrical conductor when solid (d) poor electrical conductor when molten (e) high melting point 2. In which of these substances are the atoms held together by polar covalent bonding? (a) S8 (b) SrCl2 (c) CsCl (d) CaF2 (e) ClF 3. Select the correct formula for a compound formed from barium and nitrogen. (a) Ba3N2 (b) Ba2N (c) Ba2N3 (d) BaN (e) BaN2 4. Select the element with the lowest electronegativity. (a) Li (b) Al (c) Cl (d) Cs (e) Ca 5. Select the compound with the highest lattice energy. (a) BaO (b) NaI (c) LiBr (d) MgO (e) CaS 2 of 9
6. Select the most polar bond amongst the following. (a) C O (b) Si F (c) Cl F (d) C F (e) C I 7. Select the element whose Lewis dot structure is correct. (a) (b) (c) (d) (e) 8. Which of the following contains ionic bonding? (a) SrF2 (b) CO2 (c) H2O (d) HF (e) Al 9. In which one of the following species is the central atom (the first atom in the formula) an exception to the octet rule? (a) SF6 (b) NH3 (c) NH4 + (d) I2 (e) BH4 10. Select the correct Lewis structure for ClCN. (a) (b) (c) (d) (e) 3 of 9
11. In which of the molecules below does the central atom have an sp 3 d 2 orbital hybridization? (a) XeF2 (b) H2O (c) CH4 (d) XeF4 (e) SO4 2 12. Oxygen difluoride is a powerful oxidizing and fluorinating agent. Select its Lewis structure. (a) (b) (c) (d) (e) None of the above are correct. 13. The electronic structure of the CO3 2- molecule is best represented as a resonance hybrid of equivalent structures and what is the formal change of C? (a) 2, +1 (b) 3, +2 (c) 4, +2 (d) 3, 0 (e) This molecule does not exhibit resonance, +1 14. In which of the following is the best Lewis structure a resonance structure? (a) SO3 (b) BF3 (c) I3 (d) SCO (C is the central atom) (e) SO3 2-15. The formal charge on Cl in the structure shown for the perchlorate ion is (a) -2 (b) +1 (c) 0 (d) -1 (e) +2 4 of 9
16. Considering all the bonds in a molecule with trigonal bipyramidal geometry, what are the bond angles present? (a) 120 º only (b) 90 º only (c) 90 º, 120 º, and 180 º (d) 60 º and 90 º only (e) 180 º only 17. Estimate the heat of reaction at 298 K for the reaction shown, given the average bond energies below: 2H2(g) + O2(g) 2H2O(g) H-H O=O H-O Bond Energy (kj/mol) 436 499 463 (a) 1371 kj (b) -481 kj (c) 935 kj (d) -926 kj (e) -1353 kj 18. What is the molecular shape of BCl3 as predicted by VSEPR theory? (a) linear (b) tetrahedral (c) trigonal planar (d) trigonal pyramidal (e) none of the above 19. What is the molecular shape of NO2 as predicted by the VSEPR theory? (a) bent (b) tetrahedral (c) T-shaped (d) trigonal pyramidal (e) linear 20. What is the molecular shape of XeO2F2 as predicted by the VSEPR theory? (a) square planar (b) see-saw (c) tetrahedral (d) square pyramidal (e) octahedral 5 of 9
21. Which one of the following molecules and ions will have a square planar geometry as predicted by the VSEPR theory? (a) PCl3 (b) BF4 (c) XeF4 (d) BrF5 (e) H3O + 22. What is the hybridization of the central atom in a molecule of NH3? (a) sp (b) sp 2 (c) sp 3 (d) sp 3 d (e) sp 3 d 2 23. What is the molecular structure and electron pair geometry of H2S? (a) Trigonal bipyramidal and Linear (b) Linear and Tetrahedral (c) Bent and Tetrahedral (d) Tetrahedral and Bent (e) Linear and Linear (f) 24. 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. 25. The perchloric acid (HClO4) molecule contains? (a) 13 lone pairs, 1 pi bond, and 4 sigma bonds. (b) 9 lone pairs, no pi bonds, and 6 sigma bonds. (c) 8 lone pairs, 2 pi bonds, and 7 sigma bonds (d) 8 lone pairs, 3 pi bonds, and 5 sigma bonds. (e) 11 lone pairs, no pi bonds, and 5 sigma bonds. 26. 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 6 of 9
(e) none of these 27. Which of the following molecules is non-polar? (a) H2O (b) XeF4 (c) BrCl3 (d) CH3CH2OH (e) CH3Cl 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. 28. How many lone pairs of electrons are there on a molecule of Ibuprofen? (a) 4 (b) 5 (c) 6 (d) 8 (e) 10 29. How many of the carbon atoms in a Ibuprofen molecule have sp 2 hybridization? (a) 3 (b) 4 (c) 5 (d) 6 (e) 7 30. How many pi (π) bonds are there on the molecule of Ibuprofen? (a) 2 (b) 4 (c) 6 (d) 8 (e) 10 31. How many carbon atoms in the Ibuprofen structure adopts the sp 3 hybridization? (a) 2 (b) 3 (c) 4 (d) 5 (e) 6 7 of 9
Use the molecular orbital diagrams below to answer the following 4 questions. 32. Which of the molecules listed below does not have a bond order of 2? (a) O2 (b) F2 2+ (c) ONe (d) C2 (e) CN + 33. For the molecular N2 +. The number of electrons in the σ 2p molecular orbital is (a) 0 (b) 1 (c) 2 (d) 3 (e) 4 34. What is the bond order for a molecule of O2 +? (a) 0.5 (b) 1 (c) 1.5 (d) 2 (e) 2.5 35. For the molecule B2, the number of unpaired electrons is (a) 0 (b) 1 (c) 2 (d) 3 (e) 4 8 of 9
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) sp 2 hybrid orbitals (e) sp 3 hybrid orbitals 9 of 9