Class: Date: Chapter 9 practice questions Multiple Choice Identify the choice that best completes the statement or answers the question. 1. All of the following statements concerning valence bond (VB) and molecular orbital (MO) bonding theories are correct EXCEPT a. MO theory predicts that electrons are delocalized over the molecule. b. VB theory predicts that oxygen is paramagnetic, MO theory does not. c. VB theory describes a molecular bond as the overlap between two atomic orbitals. d. in VB theory, bonding electrons are localized between pairs of atoms. e. MO theory can describe molecular bonding in excited states. 2. How many sigma (σ) bonds and pi (π) bonds are in the following molecule? a. seven σ and two π b. six σ and two π c. eleven σ and zero π d. nine σ and two π e. two σ and nine π 3. How many sigma (σ) bonds and pi (p) bonds are in acetone? a. eight σ and one π b. six σ and one π c. nine σ and one π d. one σ and nine π e. one σ and eight π 4. How many sigma (σ) bonds and pi (π) bonds are in formaldehyde, H 2 CO? a. one σ, one π b. two σ, one π c. three σ, one π d. four σ, zero π e. two σ, two π 1
5. In order to form a set of sp hybrid orbitals, how many pure atomic orbitals must be mixed? a. one s, one p b. two s, one p c. two s, two p d. one s, two p e. zero s, two p 6. In order to form a set of sp 3 d hybrid orbitals, how many pure atomic orbitals must be mixed? a. one s, one p, and one d b. one s, three p, and one d c. two s, one p, and two d d. two s, six p, and two d e. none of the above 7. What is the maximum number of hybridized orbitals that can be formed by a nitrogen atom? a. 1 b. 2 c. 3 d. 4 e. 6 8. What is the maximum number of hybridized orbitals that can be formed by xenon? a. 0 b. 2 c. 4 d. 5 e. 6 9. In which of the following molecules does the carbon atom have sp hybridization: HCN, CH 4, CO 2, and CH 2 O? a. CH 4 only b. CH 4 and CH 2 O c. HCN and CH 2 O d. HCN and CO 2 e. HCN, CO 2, and CH 2 O 10. In which of the following molecules or ions does the central atom have sp 3 hybridization: SO 2-4, XeF 4, ICl 4-, and NH 3? a. SO 2-4 and NH 3 b. SO 2-4 and ICl - 4 c. XeF 4 and NH 3 d. ICl - 4 and NH 3 e. XeF 4, ICl 4-, and NH 3 11. In which of the following molecules or ions does the central atom have sp 2 hybridization: NH 2-, H 2 O, BH 3, SO 2? a. NH - 2 and BH 3 b. H 2 O and SO 2 c. H 2 O, BH 3, and SO 2 d. NH 2-, H 2 O, and SO 2 e. BH 3 and SO 2 2
12. What is the hybridization of each oxygen atom in O 2? 13. What is the hybridization of the bromine atom in BrF 5? 14. What is the hybridization of the central nitrogen in N 3-? 15. What is the hybridization of the sulfur atom in sulfate ion, SO 2-4? 16. What is the hybridization of the central atom in a molecule with a square planar molecular geometry? 17. What is the hybridization of the central atom in a molecule with a see-saw molecular geometry? 18. What is the molecular geometry around an atom that is sp 3 hybridized and has two lone pairs of electrons? a. bent b. linear c. trigonal pyramidal d. trigonal planar e. trigonal bipyramidal 19. What is the molecular geometry around an atom that is sp 3 d 2 hybridized and has one lone pair of electrons? a. tetrahedral b. trigonal bipyramidal c. square planar d. square pyramidal e. see-saw 3
20. What is the molecular geometry around an atom that is sp 3 hybridized, has three sigma bonds, no pi bonds, and one lone pair? a. bent b. linear c. trigonal pyramidal d. trigonal planar e. tetrahedral 21. What is the molecular geometry around an atom that is sp hybridized, has two sigma bonds, two pi bonds, and no lone pairs? a. bent b. linear c. trigonal planar d. tetrahedral e. octahedral 22. In the addition of Cl 2 to PCl 3 to form PCl 5, what change in hybridization (if any) occurs to the phosphorus atom? to sp 2 to sp 3 to sp 3 d d. sp 3 to sp 3 d 2 e. no change 23. One product of the combustion of methane is carbon dioxide. What change in hybridization of the carbon occurs in this reaction? 3 to sp 2 b. sp 3 to sp to sp 3 d d. sp 2 to sp 3 d 2 e. sp 2 to sp 24. Which of the following hybridized atoms is not possible? a. an sp hybridized oxygen atom b. an sp 3 hybridized nitrogen atom c. an sp 2 hybridized carbon atom d. an sp 2 hybridized boron atom e. an sp 3 d 2 hybridized fluorine atom 25. Which of the following characteristics apply to PH 3? 1. trigonal pyramidal molecular geometry 2. sp 2 hybridized 3. polar bonds 4. nonpolar molecule a. 1 and 3 b. 2 and 4 c. 1 and 2 d. 1, 2, and 3 e. 1, 2, 3, and 4 4
26. The carbonate ion is known to be planar with all the oxygen atoms equidistant from the central carbon atom. On the basis of these facts, which of the following conclusions are true concerning this ion? 1. It can be represented by three equivalent resonance structures. 2. The carbon atom is sp 2 hybridized. 3. The dipoles associated with each C-O bond are equal in magnitude. a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3 27. For which of the following compounds do cis and trans isomers exist? a. 1 only b. 2 only c. 3 only d. 1 and 2 e. 1, 2, and 3 28. Which of the underlined atoms (N, C 1, C 2, and O) are sp 2 hybridized? a. N and O b. N, C 1, and O c. C 1, and C 2 d. O and C 1 e. O only 29. All of the following statements concerning molecular orbital (MO) theory are correct EXCEPT a. the Pauli exclusion principle is obeyed. b. electrons are assigned to orbitals of successively higher energy. c. Hund's rule is obeyed. d. a bonding molecular orbital is lower in energy than its parent atomic orbital. e. the combination of two atomic orbitals creates one molecular orbital. 5
30. Atomic orbitals combine most effectively to form molecular orbitals when a. the atomic orbitals are not hybridized. b. the atomic orbitals have similar energies. c. electrons in the orbitals have the same spin. d. electrons in the orbitals have no spins. e. the atomic orbitals have the same hybridization. 31. An electron orbital that decreases the electron density between two nuclei is said to be. a. nonbonding b. bonding c. hybridized d. antibonding e. dipolar 32. Which substance has cations bonded together by mobile electrons? a. KCl(s) b. O 2 (g) c. Mg(s) d. Si e. SiO 2 33. In order to create an n-type semiconductor, a silicon crystal could be doped with. a. Al b. C c. He d. Pb e. As Completion Complete each statement. 34. In valence bond theory, a π bond is described as the sideways overlap of two unhybridized orbitals. 35. What is the hybridization of the xenon atom in XeOF 4? 6
Chapter 9 practice questions Answer Section MULTIPLE CHOICE 1. B 2. D 3. C 4. C 5. A 6. B 7. D 8. E 9. D 10. A 11. E 12. B 13. E 14. A 15. C 16. E 17. D 18. A 19. D 20. C 21. B 22. C 23. B 24. E 25. A 26. E 27. B 28. C 29. E 30. B 31. D 32. C 33. E COMPLETION 34. p 35. sp 3 d 2 1