Chemistry & Chemical Reactions Kotz9e TB 08 PDF

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Chemistry & Chemical Reactions Chapter 8...

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Chapter 8—Bonding and Molecular Structure MULTIPLE CHOICE 1. Which of the following groups contains no ionic compounds? a. HCN, NO2, Ca(NO3)2 b. PCl5, LiBr, Zn(OH)2 c. KOH, CCl4, SF4 d. NaH, CaF2, NaNH2 e. CH2O, H2S, NH3 ANS: E 2. Which combination of atoms is most likely to produce a compound with ionic bonds? a. B and C b. S and O c. N and F d. Si and Cl e. Mg and O ANS: E 3. Which combination of atoms is most likely to produce a compound with covalent bonds? a. K and Br b. Al and S c. S and Cl d. Sn and F e. Li and I ANS: C 4. In which pair do both compounds exhibit predominantly ionic bonding? a. KI and O3 b. NaF and H2O c. PCl3 and HF d. Na2SO3 and CH4 e. RbBr and CaO ANS: E

5. Which of the following statements is/are CORRECT? 1. Ionic bonds form when one or more valence electrons are transferred from one atom to another. 2. Covalent bonds involve sharing of electrons between atoms. 3. In most covalently bonded compounds, electrons are NOT shared equally between the atoms. a. 1 only ANS: E

b. 2 only

c. 3 only

d. 1 and 2

e. 1, 2, and 3

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6. Which of the following statements is/are CORRECT? 1. Chemical reactions result in the gain, loss, or rearrangement of valence electrons. 2. For main group elements, the number of valence electrons equals eight minus the element’s group number. 3. Core electrons are not involved in bonding or in chemical reactions. a. 1 only

b. 2 only

c. 3 only

d. 1 and 3

e. 1, 2, and 3

d. 3

e. 8

ANS: D 7. An atom of Se has ____ valence electrons. a. 2 b. 6 c. 4 ANS: B

8. The following representation of an atom is called

a. b. c. d. e.

a Lewis dot structure. an ion. a structural formula. an electrostatic potential map. an ionic bond.

ANS: A

9. In the Lewis formula for sulfur dioxide, SO2, the number of lone pairs of electrons around the sulfur atom is a. 0. b. 1. c. 2. d. 3. e. 4. ANS: B

10. How many lone pairs of electrons are assigned to the iodine atom in ICl? a. 0 b. 1 c. 2 d. 3

e. 4

ANS: D

11. What is the total number of electrons (both lone and bond pairs) in the Lewis structure of C 2O4? a. 30 b. 34 c. 32 d. 46 e. 44 ANS: B

12. How many valence electrons are present in the Lewis formula for the hypochlorite ion, a. 20 b. 12 c. 18 d. 14 e. 16 ANS: D

?

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13. Which of the following molecules or ions are isoelectronic: SO 3, NF3, NO3–, CO32–? a. SO3 and NF3 b. NF3 and CO32– c. SO3, NF3 and CO32– d. SO3, NO3– and CO32– e. SO3, NF3, NO3–, and CO32– ANS: D 14. If two or more species have the same number of electrons, resulting in similar Lewis structures, they are said to be ____. a. isoelectronic b. resonant structures c. ionic d. neutral e. covalent ANS: A 15. Which of the following has a Lewis structure similar to CS2? b. O3 c. NO2 d. SO2 a. NH2

e. ClO2 

ANS: C

16. Which of the following molecules or ions will have a Lewis structure most like that of phosphorus trichloride, PCl3? a. ClO3– c. CO32– e. Cl2CO b. SO3 d. BF3 ANS: A 17. The correct Lewis structure for Cl2CO is (the 2 Cl's and the O are bound to the C and not to each other): a.

c.

b.

d.

e. none of these

ANS: A 18. Which of the following is a correct Lewis electron-dot formula for CO? a. b. c. d.

e.

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ANS: A

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19. Which of the following is a correct Lewis structure for H2SO4? a. c. e.

b.

d.

ANS: A 20. Which of the following is a correct Lewis structure for sulfate ion? a. c. e.

b.

ANS: A

d.

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21. Which is the best Lewis structure of CH2FCO2H (connectivity correct as given)? a.

d.

b.

e. none of these is acceptable

c.

ANS: D 22. How many hydrogen atoms are needed to complete the following hydrocarbon structure?

a. 4

b. 6

c. 2

d. 8

e. 3

ANS: B

23. Which of the following is the correct Lewis dash formula for carbon diselenide? a. c. e. b.

ANS: B

d.

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24. Which of the following is a correct Lewis structure for oxygen? a. b. c. d. e. ANS: A 25. All of the following Lewis structures of nitrogen oxides are possible EXCEPT

a. b. c. d. e.

N2O. N2O4. N2O3. N2O5. All of the above are correct structures.

ANS: C 26. Which of the following are possible Lewis structures for C2H6O?

a. 1

b. 2

ANS: D 27. The molecule H2S has a. b. c. d. e.

2 bonding pairs and 3 lone pairs 2 bonding pairs and 2 lone pairs 3 bonding pairs and 1 lone pair 3 bonding pairs and 3 lone pairs none of these

ANS: B

c. 3

d. 2 and 3

e. 1, 2, and 3

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28. The nitrogen atom in cyanide ion, CN–, is surrounded by a. one single bond and three lone pairs of electrons. b. one double bond and one lone pair of electrons. c. one double bond and two lone pairs of electrons. d. one triple bond and one lone pair of electrons. e. one triple bond and no lone pairs of electrons. ANS: D 29. The central atom in N2O is a nitrogen atom. This nitrogen atom is surrounded by a. two single bonds and two lone pairs of electrons. b. two single bonds and one lone pair of electrons. c. one single bond, one double bond, and one lone pairs of electrons. d. one single bond, one double bond, and one lone pair of electrons. e. two double bonds and no lone pairs of electrons. ANS: E 30. How many different molecules have the molecular formula C6H14? a. 1 b. 2 c. 3 d. 4

e. 5

ANS: E

31. Which of the following is/are true concerning formal charge? 1. The formal charge of each individual atom in a molecule or ion is an actual atomic charge that can be experimentally determined. 2. The formal charge of each individual atom is always the same for each possible resonance form. 3. The sum of the formal charges of each atom in a molecule or ion equal the overall charge of the molecule or ion. a. 1 only

b. 2 only

c. 3 only

d. 1 and 2

e. 1 and 3

d. -1

e. -2

ANS: C 32. What is the formal charge on carbon in CH2Cl2? a. +2 b. +1 c. 0 ANS: C

33. What is the formal charge on each atom in dichloromethane, CH2Cl2? a. C atom = 0, each H atom = 0, and each Cl atom = 0 b. C atom = –2, each H atom = +1, and two Cl atoms = 0 c. C atom = +4, each H = –1, and each Cl atom = –1 d. C atom = +4, each H = +1, and each Cl atom = –1 e. C atom = –4, each H = +1, and each Cl atom = +1 ANS: A

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34. What is the formal charge on atom N in the following Lewis structure?

a. 2

b. 1

c. 0

d. -1

e. -2

ANS: B

35. What is the formal charge of the carbon atom in the Lewis structure for isocyanate shown below?

a. 0

b. 2

c. +1

d. 1

e. -3

ANS: E 36. One resonance structure for OCN– ion is drawn below. What is the formal charge on each atom?

a. b. c. d. e.

O atom = 0, C atom = 0, and N atom = 0 O atom = 0, C atom = 0, and N atom = –1 O atom = –1, C atom = 0, and N atom = 0 O atom = –1, C atom = –1, and N atom = +1 O atom = +1, C atom = 0, and N atom = –2

ANS: C 37. Which of the following is not a valid resonance structure for N 3–? a.

b.

c.

d.

e. all are correct ANS: A

TOP:

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38. Which of the following are resonance structures for formate ion, HCO2–?

a. 1 and 2

b. 2 and 3

c. 3 and 4

d. 1, 3, and 4

e. 2, 3, and 4

d. NH3

e. none

ANS: C 39. Which of the following exhibits resonance? a. SCl6 b. H2O c. SO2 ANS: C

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40. Which of the following molecules or ions does not have one or more resonance structures? d. H2CO a. O3 b. OCN– c. SO2 e. NO3– ANS: D 41. The Lewis structure of which of the following formula violates the octet rule? a. SF6 b. NF3 c. OF2 d. HF e. SiF4 ANS: A

42. Which of the following elements is able to form a molecular structure that exceeds the octet rule? a. F b. N c. C d. B e. Sb ANS: E

43. Which of the following elements is most likely to form a molecular structure that disobeys the octet rule? a. B b. C c. N d. O e. F ANS: A 44. When both of the electrons in a molecular bond originate from the same atom, the bond is called a(n) a. sigma bond. b. coordinate covalent bond. c. pi bond. d. metallic bond. e. ionic bond. ANS: B 45. In the Lewis structure of SF6, how many lone pairs are around the central atom? a. 0 b. 1 c. 2 d. 3 e. 4 ANS: A

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46. Which of the following has an incomplete octet in its Lewis structure? a. SO2 b. F2 c. NO2 d. ICl

e. CO2

ANS: C

47. What is the correct Lewis structure for SF4? a. c.

b.

e.

d.

ANS: C 48. What is the correct Lewis structure for IF3? a. c.

b.

e.

d.

ANS: E 49. When you draw the Lewis structure for PF2Cl3, how many single bonds, double bonds, and lone pair electrons reside on the central phosphorus atom? a. 5 single bonds, 0 double bonds, 0 lone pairs b. 4 single bonds, 1 double bond, 0 lone pairs c. 5 single bonds, 0 double bonds, 1 lone pair d. 4 single bonds, 1 double bond, 1 lone pair e. 3 single bonds, 2 double bonds, 0 lone pairs ANS: A

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50. The central atom in SF6 is surrounded by a. six single bonds and no lone pairs of electrons. b. six single bonds and one lone pair of electrons. c. six single bonds and two lone pairs of electrons. d. five single bonds, one double bond, and one lone pair of electrons. e. four single bonds, two double bonds, and no lone pairs of electrons. ANS: A 51. Which of the following species will have a Lewis structure most like that of IF4–? a. XeF4 b. SO42– c. PF4+ e. IO4– d. SF4 ANS: A 52. Which of the following molecules or ions are likely to be free radicals: N 2O, NO, and NO2? a. N2O only b. NO only c. NO2 only d. N2O and NO e. NO and NO2 ANS: E 53. What is the molecular geometry around an atom in a molecule or ion which is surrounded by zero lone pairs of electrons and four single bonds. a. tetrahedral b. linear c. bent d. trigonal pyramidal e. trigonal planar ANS: A 54. What is the electron-pair geometry around an atom in a molecule or ion which is surrounded by zero lone pairs of electrons and five single bonds. a. trigonal bipyramidal b. see-saw or distorted tetrahedron c. T-shaped d. linear e. trigonal planar ANS: A

55. What is the bond angle in a trigonal planar molecule or ion? a. 109° b. 180° c. 90° d. 72° ANS: E

e. 120°

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56. What is the molecular geometry around oxygen atom O2?

a. b. c. d. e.

linear trigonal pyramidal trigonal planar T-shaped tetrahedral

ANS: A

57. What is the molecular geometry around carbon atom C3?

a. b. c. d. e.

linear tetrahedral trigonal planar trigonal pyramidal square planar

ANS: B

58. Use VSEPR theory to predict the electron-pair geometry and the molecular geometry of nitrogen trichloride, NCl3. a. The electron-pair geometry is linear, the molecular geometry is linear. b. The electron-pair geometry is trigonal-planar, the molecular geometry is trigonal-planar. c. The electron-pair geometry is trigonal-planar, the molecular geometry is bent. d. The electron-pair geometry is tetrahedral, the molecular geometry is tetrahedral. e. The electron-pair geometry is tetrahedral, the molecular geometry is trigonal-pyramidal. ANS: E

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59. Use VSEPR theory to predict the electron-pair geometry and the molecular geometry of boron tribromide, BBr3. a. The electron-pair geometry is trigonal-pyramidal, the molecular geometry is trigonalpyramidal. b. The electron-pair geometry is trigonal-planar, the molecular geometry is trigonal-planar. c. The electron-pair geometry is trigonal-planar, the molecular geometry is bent. d. The electron-pair geometry is tetrahedral, the molecular geometry is trigonal-pyramidal. e. The electron-pair geometry is trigonal-pyramidal, the molecular geometry is t-shaped. ANS: B 60. Use VSEPR theory to predict the electron-pair geometry and the molecular geometry of sulfur dioxide, SO2. a. The electron-pair geometry is trigonal-planar, the molecular geometry is trigonal-planar. b. The electron-pair geometry is trigonal-planar, the molecular geometry is bent. c. The electron-pair geometry is tetrahedral, the molecular geometry is bent. d. The electron-pair geometry is tetrahedral, the molecular geometry is linear. e. The electron-pair geometry is trigonal-bipyramidal, the molecular geometry is linear. ANS: B 61. Use VSEPR theory to predict the electron-pair geometry and the molecular geometry of sulfur dioxide, XeF4. a. The electron-pair geometry is tetrahedral, the molecular geometry is tetrahedral. b. The electron-pair geometry is octahedral, the molecular geometry is tetrahedral. c. The electron-pair geometry is tetrahedral, the molecular geometry is octahedral. d. The electron-pair geometry is octahedral, the molecular geometry is square-planar. e. The electron-pair geometry is square-planar, the molecular geometry is tetrahedral. ANS: D 62. Use VSEPR theory to predict the molecular geometry of BrO3–. a. trigonal-pyramidal b. trigonal-planar c. bent d. T-shaped e. linear ANS: A 63. Use VSEPR theory to predict the molecular geometry around either carbon atom in acetylene, C2H2. a. linear b. bent c. trigonal-planar d. tetrahedral e. octahedral ANS: A

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64. Use VSEPR theory to predict the molecular geometry around the carbon atom in formaldehyde, H 2CO. a. linear b. bent c. trigonal-planar d. tetrahedral e. octahedral ANS: C 65. Use VSEPR theory to predict the molecular geometry of BrF5. a. tetrahedral b. see-saw c. trigonal-bipyramidal d. square-pyramidal e. octahedral ANS: D 66. Use VSEPR theory to predict the molecular geometry around the nitrogen atom in nitrite ion, NO2–. a. trigonal-planar b. tetrahedral c. trigonal-pyramidal d. T-shaped e. bent ANS: E 67. Based on electron geometries, which of the following molecules has the smallest bond angle between any two adjacent hydrogen atoms? a. CH4 b. H2O c. BH3 d. PH3 e. SF6 ANS: E 68. What are the approximate HNH bond angles in NH4+? a. 109.5 b. 120 c. 109.5 and 120 d. 90 e. 90 and 120 ANS: A 69. What is the OCN bond angle in OCN–? a. 90 b. 107 c. 109.5 ANS: E

d. 120

e. 180

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70. What are the approximate OSO bond angles in SO32–? a. 90 b. 109.5 c. 120 d. 180 e. 90 and 180 ANS: B 71. What are the approximate FBrF bond angles in BrF5? a. 90 and 180 b. 109.5 c. 90 and 120 d. 120 e. 180 ANS: A 72. Place the following molecules in order from smallest to largest HNH bond angles: NH4+, NH3, and NH2–. a. NH4+ < NH3 < NH2– b. NH4+ < NH2– < NH3 c. NH2– < NH3 < NH4+ d. NH2– < NH4+ < NH3 e. NH3 < NH2– < NH4+ ANS: C 73. Which of the following bonds would be the most polar? a. N—N

b. N—P

c. N—C

d. N—As

e. N—Ge

ANS: E

74. Which of the following compounds has polar covalent bonds: CCl4, Cl2, HCl, and KCl? a. CCl4 only b. Cl2 only c. HCl and KCl d. Cl2 and KCl e. CCl4 and HCl ANS: E 75. Electronegativity is a measure of a. the ability of a substance to conduct electricity. b. the charge on a polyatomic cation. c. the charge on a polyatomic anion. d. the ability of an atom in a molecule to attract electrons to itself. e. the oxidation number of an atom in a molecule or polyatomic anion. ANS: D

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76. Three non-equivalent Lewis structures for carbonyl sulfide, SCO, are given below. Use the concepts of formal charge and electronegativity to choose the structure that is the best representation.

A a. b. c. d. e.

B

C

Structure A, because all the formal charges equal 0. Structure B, because all the formal charges equal 0. Structure C, because all the formal charges equal 0. Structure A, because the negative formal charge resides on the most electronegative atom. Structure C, because the negative formal charge resides on the most electronegative atom.

ANS: B 77. Choose which central atom in the following molecules is most electronegative. a. PH3 b. CH4 c. H2S d. H2O e. NH3 ANS: D 78. Rank the following covalent bonds in order of decreasing polarity: C-H, N-H, O-H, F-H. a. F-H, O-H, N-H, C-H b. O-H, F-H, N-H, C-H c. N-H, F-H, O-H, C-H d. C-H, N-H, O-H, F-H e. C-H, F-H, O-H, N-H ANS: A 79. Atoms having equal or nearly equal electronegativities are expected to form a. no bonds b. polar covalent bonds c. nonpolar covalent bonds d. ionic bonds e. covalent bonds ANS: C 80. Which of the following molecules is nonpolar? a. sulfur dioxide, SO2 b. phosphorus trifluoride, PF3 c. hydrogen fluoride, HF d. phosphorus pentafluoride, PF5 e. nitrogen trifluoride, NF3 ANS: D

81. Which one of the following molecules is polar? a. CS2 b. SO2 c. XeF2 ANS: B

d. XeF4

e. SO3

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82. Three possible structures of C2H2Cl2 are shown below. Which of these molecules are polar?

a. 1 only

b. 2 only

c. 3 only

d. 1 and 3

e. 2 and 3

ANS: D 83. Linus Pauling noticed that the energy of a polar bond is often greater than expected. He attributed the greater bond energy to a. a coulombic attraction between atoms with partially positive and negative charges. b. the greater bond lengths of the heteronuclear bonds. c. one of the many unexplainable phenomena that scientists encounter. d. the ability of heteronuclear species to form double and triple bonds. e. the greater number of valence electrons found in heteronuclear molecules. ANS: A 84. In molecules, as bond order increases, a. both bond length and bond energy increase. b. both bond length and b...