Organic Chemistry TEST BANK - Chapter 1 MULTIPLE CHOICE...

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Unformatted text preview: Chapter 1 MULTIPLE CHOICE QUESTIONS Topic: Atomic Orbitals 1. A) B) C) D) E) In quantum mechanics a node (nodal surface or plane) is: a place where Ψ is negative. a place where Ψ is positive. a place where Ψ = 0. a place where Ψ2 is large. a place where Ψ2 is negative. Ans: C Topic: Atomic Orbitals, Molecular Orbitals 2. When the 1s orbitals of two hydrogen atoms combine to form a hydrogen molecule, how many molecular orbitals are formed? A) 1 B) 2 C) 3 D) 4 E) 5 Ans: B Topic: Atomic Orbitals 3. Which principle(s) or rule must be used to determine the correct electronic configuration for carbon in its ground state? A) Aufbau Principle B) Hund's Rule C) Pauli Exclusion Principle D) (A) and (B) only E) All three Ans: E 1 Chapter 1 Topic: Atomic Orbitals, Bonding 4. What point on the potential energy diagram below represents the most stable state for the hydrogen molecule? A) B) C) D) E) I II III IV V Ans: C Topic: Atomic Orbitals, Molecular Orbitals 5. A) B) C) D) E) According to molecular orbital theory, which molecule could not exist? H2 He2 Li2 F2 N2 Ans: B Topic: Atomic Orbitals, Molecular Orbitals 6. When the ls orbitals of two hydrogen atoms combine to form a hydrogen molecule, which molecular orbitals are formed? A) One bonding molecular orbital only B) Two bonding molecular orbitals C) One bonding molecular orbital and one antibonding molecular orbital D) Two antibonding molecular orbitals E) Three bonding molecular orbitals Ans: C 2 Chapter 1 Topic: Atomic Orbitals, Hybridization 7. The following electron configuration represents _______. A) B) C) D) E) 1s 2sp3 2sp3 2sp3 2sp3 the ground state of boron. the sp3 hybridized state of carbon. the sp3 hybridized state of nitrogen. the ground state of carbon. an excited state of carbon. Ans: C Topic: Atomic Orbitals, Molecular Orbitals 8. According to molecular orbital theory, in the case of a carbon-carbon double bond, the carbon-carbon bonding electrons of higher energy occupy this molecular orbital. A) σ bonding MO B) π bonding MO C) σ* antibonding MO D) π* antibonding MO E) π* bonding MO Ans: B Topic: Atomic Orbitals, Hybridization 9. A) B) C) D) E) Identify the atomic orbitals in the C-C sigma bond in ethyne. (2sp2, 2sp2) (2sp3, 2sp3) (2sp, 2sp) (2p, 2p) (2sp, 1s) Ans: C 3 Chapter 1 Topic: Lewis Structures, Formal Charges 10. Listed below are electron dot formulas for several simple molecules and ions. All valence electrons are shown; however, electrical charges have been omitted deliberately. H : Be : H H .. H:N:H .. H .. H:N:H .. H H .. H:O:H .. I A) B) C) D) E) H .. H:B:H .. H II III IV V Which of the structures actually bear(s) a positive charge? I II III III & V IV & V Ans: E Topic: Lewis Structures, Formal Charges 11. What is the formal charge on oxygen in the following structure? .. H3C O CH3 CH3 A) B) C) D) E) +2 +1 0 -1 -2 Ans: B 4 Chapter 1 Topic: Lewis Structures, Formal Charges 12. In which structure(s) below does the oxygen have a formal charge of +1? .. H O H H .. .. O: C O H H I .. H II .. H H3C O CH3 CH3 III IV s A) B) C) D) E) I only II only I and III I and IV I, III, and IV Ans: E Topic: Lewis Structures, Formal Charges 13. Which structure(s) contain(s) an oxygen that bears a formal charge of +1? .. .. :O :O .. .. .. .. : O C O: H C H3C O H H3C O CH3 C : O. : : O. : : O. : . . . CH3 H I II III IV V A) B) C) D) E) I and II III and IV V II I and V Ans: B 5 Chapter 1 Topic: Lewis Structures, Formal Charges 14. Which of the following molecules or ions has a nitrogen with a formal charge of -1? (Charges on ions have been omitted.) .. A) : N H H B) H C) H .. N .H . N H D) H3C H CH3 .. N H E) H3C C Ans: A CH3 N: Topic: Lewis Structures, Formal Charges 15. In which structure(s) below does nitrogen have a formal charge of +1? H3C N CH2 H3C .. N .. H .. H N H .. OH .. .. H3C NH2 H I A) B) C) D) E) .. H3C N CH3 II III I II and IV III and V I and V V Ans: A 6 IV V CH3 Chapter 1 Topic: Lewis Structures, Formal Charges 16. Which of the following is an ion with a single negative charge? .. A) H3C O : . . .. . .. . B) : O N O : .. .. C) : O: .. :O N : O. : . D) All of these E) None of these Ans: D Topic: Lewis Structures, Formal Charges 17. Which of these is a correct electron-dot representation of the nitrite ion, NO2-? .. .. .. .. .. .. .. : O : : N : : .. :O:N::O O :O::N:O: .. .. .. .. .. I III II .. .. .. :O:N:O: .. .. IV A) B) C) D) E) .. .. .. :O::N:O .. .. V I II III IV V Ans: A 7 Chapter 1 Topic: Lewis Structures, Formal Charges 18. Which is NOT a correct Lewis structure? .. A) H N F : .. H H B) H C) H H .. O .. .. F: .. C D) H .. O .. .. O H . .. . :O H B : O. H . E) None of these Ans: A Topic: Lewis Structures, Formal Charges 19. Listed below are electron dot formulas for several simple molecules and ions. All valence electrons are shown; however, electrical charges have been omitted deliberately. H : Be : H H .. H:N:H .. H .. H:N:H .. H H .. H:O:H .. I A) B) C) D) E) H .. H:B:H .. H II III IV V Which of the structures is negatively charged? I II III IV V Ans: B 8 Chapter 1 Topic: Lewis Structures, Formal Charges 20. Which compound contains a nitrogen atom with a formal positive charge? N H N I A) B) C) D) E) N II III I II III More than one of the above None of the above Ans: D Topic: Lewis Structures 21. Considering Lewis structures, which of these compounds possesses a single unpaired electron? A) N2 B) N2O C) NO D) N2O4 E) O2 Ans: C Topic: Lewis Structures .. 22. Z Y A) B) C) D) E) .. Y is a generalized structural representation which can be used for all of the following, except: OF2 NH2– H2S BeBr2 There is no exception Ans: D 9 Chapter 1 Topic: Lewis Structures, Formal Charges 23. In which of these cases does the central atom have a zero formal charge? A) HFH H B) C) H3C O F F B CH3 F F H D) H3C N CH3 H CH3 E) H3C C CH3 CH3 Ans: E Topic: Lewis Structures, Formal Charges 24. The formal charge on sulfur in sulfuric acid is: O H O S O H O A) B) C) D) E) 0 -1 +1 -2 +2 Ans: A Topic: Lewis Structures, Formal Charges 25. ExpAns:ion of the valence shell to accommodate more than eight electrons is possible with: A) Fluorine B) Nitrogen C) Carbon D) Sulfur E) Beryllium Ans: D 10 Chapter 1 Topic: Lewis Structures, Molecular Geometry 26. A) B) C) D) E) Based on VSEPR theory, which of the following would have a trigonal planar shape? CH3)3N HCN NH4+ CH3− CH3+ Ans: E Topic: Lewis Structures, Molecular Geometry 27. A) B) C) D) E) VSEPR theory predicts an identical shape for all of the following, except: NH3 H3O+ BH3 CH3All have the same geometry Ans: C Topic: Lewis Structures, Molecular Geometry 28. A) B) C) D) E) What shape does the methyl cation, CH3+, have? Octahedral Tetrahedral Trigonal planar Linear Trigonal pyramidal Ans: C 11 Chapter 1 Topic: Lewis Structures, Molecular Geometry : : 29. Which of the structures below would be trigonal planar (a planar triangle)? (Electrical charges have been deliberately omitted.) F F H .. .. .. .. .. .. :F : N : H:O:H H:C: B :..: .. .. .. .. .. F H F F H .. .. .. .. .. : .. .. : .. I A) B) C) D) E) II IV III I II III IV I and IV Ans: A Topic: Lewis Structures, Molecular Geometry 30. Which of the following would have a trigonal planar (or triangular) structure? : CH3 : NH3 BH3 : OH3 I A) B) C) D) E) : CH3 II III IV V I, II, and IV II and IV IV II, IV, and V All of these Ans: B Topic: Molecular Geometry 31. A) B) C) D) E) What bond angle is associated with a tetrahedral molecule? 120° 109.5° 180° 90° 45° Ans: B 12 Chapter 1 Topic: Molecular Geometry 32. A) B) C) D) E) What would be the spatial arrangement of the atoms of the methyl anion, :CH3-? Octahedral Tetrahedral Trigonal planar Linear Trigonal pyramidal Ans: E Topic: Lewis Structures, Molecular Geometry 33. A) B) C) D) E) Which of these structures would be a perfectly regular tetrahedron? CH3Br CH2Br2 CHBr3 CBr4 More than one of these Ans: D Topic: Lewis Structures, Molecular Geometry 34. Which molecule would be linear? (In each case you should write a Lewis structure before deciding.) A) SO2 B) HCN C) H2O2 D) H2S E) OF2 Ans: B Topic: Lewis Structures, Molecular Geometry 35. A) B) C) D) E) The bond angles in PH3 would be expected to be approximately: 60° 90° 105° 109° 120° Ans: C 13 Chapter 1 Topic: Periodic Properties, Electronegativity 36. A) B) C) D) E) Select the most electronegative element. H O N B C Ans: N Topic: Atomic Orbitals, Hybridization 37. Select the hybridized atomic orbital. I A) B) C) D) E) II III IV V I II III IV V Ans: C Topic: Atomic Orbitals, Hybridization 38. How many 2p atomic orbitals from boron must be mixed with a 2s atomic orbital to yield the bonding hybrid atomic orbitals in BF3? A) 1 B) 2 C) 3 D) 4 E) 5 Ans: B 14 Chapter 1 Topic: Atomic Orbitals, Hybridization 39. A) B) C) D) E) In which molecule is the central atom sp3 hybridized? CH4 NH3 H2O All of these None of these Ans: D Topic: Atomic Orbitals, Hybridization 40. In which of the following would you expect the central atom to be sp3 hybridized (or approximately sp3 hybridized)? A) BH4B) NH4+ C) CCl4 D) CH3:E) All of these Ans: D Topic: Atomic orbitals, hybridization 41. A) B) C) D) E) Which compound has the shortest carbon-carbon bond(s)? CH3CH3 CH2=CH2 HC≡CH CH3CH2CH3 All carbon-carbon bonds are the same length. Ans: C Topic: Atomic Orbitals, Hybridization 42. A) B) C) D) E) Which of the following contains an sp2-hybridized carbon? CH4 CH3:− CH3CH3 CH3+ HC≡CH Ans: D 15 Chapter 1 Topic: Atomic Orbitals, Hybridization 43. Which is the shortest of the carbon-carbon single bonds indicated by arrows in the following compounds? A) H3C CH3 H3C C H3C CH B) C) CH CH2 D) HC C C CH E) H2C HC C CH Ans: D Topic: Atomic Orbitals, Hybridization 44. A) B) C) D) E) How many sigma (1s-2sp3) bonds are there in ethane? 7 6 5 3 1 Ans: B Topic: Atomic Orbitals, Bonding 45. A) B) C) D) E) Which of these substances contains both covalent and ionic bonds? NH4Cl H2O2 CH4 HCN H2S Ans: A 16 Chapter 1 Topic: Atomic Orbitals, Periodic Trends, Electronegativity 46. A) B) C) D) E) The greatest degree of ionic character is anticipated for the bond between: H and C H and Cl C and Cl H and Br Br and Cl Ans: B Topic: Atomic Orbitals, Hybridization 47. A) B) C) D) Which molecule contains an sp-hybridized carbon? HCN CH2=CH2 CH3Cl H C O H E) CH3CH3 Ans: A Topic: Atomic Orbitals, Lewis structures, Resonance 48. Which of the structures below is not expected to contribute to the CO2 resonance hybrid? A) O B) C O O C C O O C) O D) E) O O C C O O Ans: D 17 Chapter 1 Topic: Atomic orbitals, Lewis structures, resonance .. : .. 49. Which of the following could not be a resonance structure of CH3NO2? A) H O H C N .. .O . H O .. B) : H H C N H .. .. H : C C) .. : .. O H N +2 O O H : O .. .. H .. : .. H D) C N.. O .. E) Both C and D Ans: D H H Topic: Atomic Orbitals, Lewis Structures, Resonance O : : : C : : : : : 50. Which of the following pairs are NOT resonance structures? A) and H3C O N O : H3C O N O : : .. .. O .. and O : C .. .. O : : B) .. .. : O N O: O : H3C : C) and H3C N .. : .. : O D) Each of these pairs represents resonance structures. E) None of these pairs represents resonance structures. Ans: C 18 Chapter 1 Topic: Atomic Orbitals, Lewis Structures, Resonance 51. How many resonance structures can be written for the NO3- ion in which the nitrogen atom bears a formal charge of +1? A) 1 B) 2 C) 3 D) 4 E) 5 Ans: C Topic: Empirical and Molecular Formulas 52. A) B) C) D) E) What is the empirical formula for cyclohexane? (Its molecular formula is C6H12.) CH CH2 C2H4 C6H6 C2H2 Ans: B Topic: Empirical and Molecular Formulas 53. A compound has the empirical formula, CCl. Its molecular weight is 285 +/- 5. What is the molecular formula for the compound? A) C2Cl2 B) C3Cl3 C) C4Cl4 D) C5Cl5 E) C6Cl6 Ans: E Topic: Empirical and Molecular Formulas 54. A compound consists only of carbon, hydrogen and oxygen. Elemental analysis gave: C, 70.5%, H, 13.8%. The molecular weight of the compound was found to be 103 +/- 3. What is the molecular formula for the compound? A) C6H12O B) C5H12O2 C) C3H2O4 D) C3H6O3 E) C6H14O Ans: E 19 Chapter 1 Topic: Isomerism 55. Which of the following is a set of constitutional isomers? Br Br I A) B) C) D) E) Br II Br III IV I and II II and III I, II, and III II, III, and IV I, III, and IV Ans: E Topic: General 56. Credit for the first synthesis of an organic compound from an inorganic precursor is usually given to: A) Berzelius B) Arrhenius C) Kekule D) Wohler E) Lewis Ans: D Topic: Isomerism 57. A) B) C) D) E) CH3CH2OCH2CH3 and CH3CH2CH2CH2OH are examples of what are now termed: Structural isomers Resonance structures Functional isomers Empirical isomers Constitutional isomers Ans: E 20 Chapter 1 Topic: Hybridization 58. What is the approximate hybridization state of the oxygen molecule in ethanol, C2H5OH? A) sp B) sp2 C) sp3 D) p3 E) d2sp3 Ans: C Topic: Hybridization 59. What is the approximate hybridization state of the oxygen molecule in trimethylamine, (CH3)3N? A) sp B) sp2 C) sp3 D) p3 E) d2sp3 Ans: C Topic: Lewis structures, Hybridization 60. Which molecule has a non-linear structure (i.e., for which molecule are the nuclei not in a straight line)? A) O=C=O B) H–O–H C) H–Cl D) H–C≡N E) H–C≡C–H Ans: B 21 Chapter 1 Topic: Isomerism 61. Which of the following structures represent compounds that are constitutional isomers of each other? I A) B) C) D) E) II III IV I and II I and III I, II, and III I, II, III, and IV II and III Ans: C Topic: Isomerism 62. Which compound is not an isomer of the others? OH O O OH I A) B) C) D) E) II III I II III IV All of the above are isomers of each other. Ans: A 22 IV Chapter 1 Topic: Isomerism 63. Consider the following: CH3CH2CH=CHCH2CH3 I CH3CH=CHCH2CH2CH3 III A) B) C) D) E) CH3CH2CH2CH2CH=CH2 II CH2=CHCH2CH2CH2CH3 IV Which two structures represent the same compound? I and II II and III I and III II and IV None of these Ans: D Topic: Isomerism 64. Consider the following: CH3CH2CH2CH=CHCH2CH2CH3 I CH3CH2CH=CHCH2CH2CH2CH3 III A) B) C) D) E) CH3CH2CH2CH2CH2CH2CH=CH2 II CH2=CHCH2CH2CH2CH2CH2CH3 IV Which structures can exist as cis-trAns: isomers? I and II I and III I and IV II and III I alone Ans: B 23 Chapter 1 Topic: Isomerism 65. Which of the following represent a pair of constitutional isomers? A) and B) CH3CH=CH2 and CH2=CHCH3 Br Br C) Br H H Br D) H and Br H Br H Br H and H H Br E) More than one of these Ans: E Topic: Isomerism 66. Which of the following represent pairs of constitutional isomers? OH O A) O and Br H Br CH3 H and Br H CH2 C) O CH3 CH3 B) H Br H and H CH3 D) More than one of these pairs E) All of these pairs Ans: D Topic: Isomerism 67. A) B) C) D) E) Cis-trAns: isomerism is possible only in the case of: CH2=CBr2 CH2=CHBr BrCH=CHBr Br2C=CHBr Br2C=CBr2 Ans: C 24 Chapter 1 Topic: Atomic orbitals, molecular orbitals 68. When the 1s orbitals of two hydrogen atoms combine to form a hydrogen molecule, how are the electrons distributed in the resulting molecular orbitals? A) 2 electrons in the bonding molecular orbital B) 1 electron in the bonding molecular orbital, 1 electron in the non-bonding molecular orbital C) 1 electron in the bonding molecular orbital, 1 electron in the antibonding molecular orbital D) 2 electrons in the non-bonding molecular orbital E) 2 electrons in the antibonding molecular orbital Ans: A Topic: Atomic Orbitals, Electron Configuration, Hybridization 69. The following electron configuration represents: A) B) C) D) E) 1s 2sp3 2sp3 2sp3 2sp3 The ground state of nitrogen The ground state of oxygen The sp3 hybridized state of carbon The excited state of oxygen None of the above correctly identifies the given electron configuration Ans: E Topic: Atomic Orbitals, Hybridization, Bonding 70. Identify the atomic orbitals involved in the C-2---C-3 sigma bond (indicated by an arrow) in the following molecule: 1 4 2 6 7 A) B) C) D) E) 5 2 3 2 sp , sp sp2, sp sp2, sp3 sp3, sp2 sp, sp2 Ans: E 25 Chapter 1 Topic: Lewis Structures 71. A) B) C) D) E) In which of the following does the central atom have 2 pairs of non-bonding electrons? O3 CO2 CO3 2− NH4+ H2S Ans: E Topic: Molecular Geometry 72. Based on the VSEPR theory, which of the following would have a tetrahedral arrangement of electrons around the central atom? A) BH3 B) NO2 − C) SiH4 D) CO3 2− E) SO3 Ans: C Topic: Molecular Geometry 73. A) B) C) D) E) What would be the spatial arrangement of the atoms of the ozone molecule (O3)? Linear Angular Trigonal planar Trigonal pyramidal Tetrahedral Ans: B Topic: Periodic Trends, Electronegativity 74. A) B) C) D) E) Select the least electronegative element P N Mg Si K Ans: E 26 Chapter 1 Topic: Atomic Orbitals, Hybridization 75. In which molecule(s) can the molecular geometry be attributed to an sp2 hybridized central atom? A) PBr3 B) CH4 C) CHCl3 D) HNO2 E) None of the above has an sp2 hybridized central atom Ans: D Topic: Bonding, Atomic Orbitals, Hybridization 76. Which molecule has the shortest carbon-carbon single bond? I II III IV A) B) C) D) E) V I II III IV V Ans: E Topic: Atomic Orbitals, Hybridization 77. How many s-sp2 bonds are there in the following substance? A) B) C) D) E) 2 3 4 5 12 Ans: B 27 Chapter 1 Topic: Atomic Orbitals, Hybridization 78. How many s-sp3 bonds are there in the following substance? A) B) C) D) E) 3 8 12 13 16 Ans: D Topic: Resonance 79. A) B) C) D) E) Which of the following species exhibits resonance stabilization? H2SO4 O3 CO2 CCl4 None of the above species exhibit resonance Ans: B SHORT ANS:WER QUESTIONS Topic: General 80. Organic compounds were originally defined as compounds obtained from __________. Ans: living sources/organisms Topic: General 81. The modern definition of organic chemistry is _________________. Ans: the study of carbon compounds Topic: General 82. Different compounds with the same molecular formula are referred to as __________. Ans: isomers 28 Chapter 1 Topic: General 83. Constitutional isomers differ in the _________________. Ans: connectivity of their atoms Topic: General 84. The bond that results when two atoms share a pair of electrons is called a _________________. Ans: covalent bond Topic: Atomic orbitals 85. Define an orbital. Ans: a region of space where the probability of finding an electron is high Topic: Atomic orbitals 86. An orbital is defined as a region of space where the probability of _________________ is high. Ans: finding an electron Topic: Atomic orbitals 87. There are three fundamental rules that we use in writing electronic configurations for atoms and molecules. The configuration shown below (for oxygen) violates one of these rules. Which one? 1s 2s 2p 2p Ans: Pauli exclusion principle 2p Topic: Molecular orbitals 88. When atomic orbitals of opposite phase overlap a(n) _________________ molecular orbital is formed. Ans: antibonding Topic: Molecular orbitals 89. When atomic orbitals of the same phase overlap a(n) _________________ molecular orbital is formed. Ans: bonding 29 Chapter 1 Topic: Lewis Structures 90. Draw the Lewis structure of the nitrite ion, NO2− , clearly indicating resonance contributors as well as non-bonding pairs of electrons and formal charges, as relevant. Ans: O . . .. .O . . .. . .. N .. . .. .. . .O . . O . N Topic: Isomers, Bond-Line Formulas 91. Draw all the isomers of C4H9Br, using bond-line formulas. Br Ans: Br Br Br Topic: Isomers, Bond-Line Formulas 92. Draw all the isomers of C4H10O, using bond-line formulas. OH Ans: OH OH O O O Topic: Isomers, Bond-Line Formulas 93. Draw all isomers of C4H8, using bond-line formulas. Ans: 30 OH Chapter 1 Topic: Lewis Structures .. .. 94. Draw the Lewis structure of acetic acid, CH3CO2H, clearly indicating all non-bonding pairs of electrons. O Ans: H H C C . .O. . H H 31 Chapter 2 MULTIPLE CHOICE QUESTIONS Topic: Intermolecular forces 1. Which compound would you expect to have the lowest boiling point? NH2 A) B) NH2 C) H N D) N E) NH2 Ans: D : Topic: Molecular geometry, dipole moment 2. Which molecule would you expect to have no dipole moment (i.e., μ = 0 D)? A) CHF3 H B) F H C) :NF3 D) F H F F H E) CH2F2...
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