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C)
O22–
D)
O2+
E)
O22+
59. The fact that O2 is paramagnetic can be explained by
A)
the Lewis structure of O2
B)
resonance
C)
a violation of the octet rule
D)
the molecular orbital diagram for O2
E)
hybridization of atomic orbitals in O2
60. For how many of the following does the bond order decrease if you add one electron to the
neutral molecule?
B2, C2, P2, F2
A)
0
B)
1
C)
2
D)
3
E)
4
61. Which of the following diatomic molecules has a bond order of 2?
A)
B2
B)
C2
C)
P2
D)
F2
E)
Li2
62. Which of the following has the largest bond order?
A)
N2
B)
N2–
C)
N22–
D)
N2+
E)
N22+
63. How many of the following: F2, B2, O2, N2 , are paramagnetic?
A)
0
B)
1
C)
2
D)
3
E)
4
64. Order the following from shortest to longest bond:
C2, B2, H2, N2
A)
H2, N2, C2, B2
B)
N2, C2, B2, H2
C)
C2, N2, H2, B2
D)
C2, B2, H2, N2
E)
none of these
65. Which charge(s) on an O2 ion would give a bond order of 2.5?
A)
–2
B)
–1
C)
+1
D)
two of these
E)
none of these
66. For how many of the following does bond order decrease if you take away one electron
from the neutral molecule?
B2, C2, P2, F2
A)
0
B)
1
C)
2
D)
3
E)
4
67. Which of the following has the shortest bond length?
A)
O22–
B)
O2
C)
O2–
D)
O2+
E)
Two of these have the shortest bond length.
68. Which of the following has a bond order of 1.5?
A)
O2+
B)
N2
C)
O2–
D)
C2
E)
none of these
69. How many unpaired electrons in the F22+ ion are based on molecular orbital theory? The
order of the molecular orbitals are (2s)(*2s)(2p)(2p)(*2p)(*2p).
A)
0
B)
1
C)
2
D)
3
E)
4
70. A species has the following MO configuration:
(1s)2(1s*)2(2s)2(2s*)2(2p)2(2p)2
This substance is
A)
paramagnetic with one unpaired electron
B)
paramagnetic with two unpaired electrons
C)
paramagnetic with three unpaired electrons
D)
paramagnetic with four unpaired electrons
E)
diamagnetic
71. What is the bond order of Ne2?
A)
0
B)
C)
1
D)
E)
2
72. What is the bond order of C2+?
A)
0
B)
C)
1
D)
E)
2
73. Which of the following statements is false?
A)
C2 is paramagnetic.
B)
C2 is diamagnetic.
C)
The carbon-carbon bond in C22– is stronger than the one in CH3CH3.
D)
The carbon-carbon bond in C22– is shorter than the one in CH3CH3.
E)
Two of the above.
74. According to MO theory, F2 should be diamagnetic.
75. The H2– ion is more stable than H2 since it has an additional electron to produce a net
lowering of energy.
76. Paramagnetism is associated with paired electrons.
77. Which of the following statements about the molecule BN is false?
A)
It is paramagnetic.
B)
Its bond order is 2.
C)
The total number of electrons is 12.
D)
It has two pi bonds.
E)
All of these are true.
78. Which of the following statements about the species CN– is false?
A)
It is paramagnetic.
B)
The total number of electrons is 14.
C)
Its bond order is 3.
D)
It has two pi bonds.
E)
All of these are true.
79. Which of the nitrogen-containing molecules below is paramagnetic in its lowest energy
state?
A)
N2
B)
NO
C)
NH3
D)
N2H4
E)
none of these
80. Which of the following statements is incorrect?
A)
For the molecule NO, the molecular orbital model is preferred over the localized
electron model because NO contains an unpaired electron.
B)
Electrons in antibonding orbitals will cause a molecule to be paramagnetic.
C)
According to the molecular orbital model, when bonding occurs between hydrogen
and bromine to make HBr, the 1s orbital of the hydrogen atom no longer exists.
D)
Antibonding electrons are higher in energy than the atomic orbitals from which
they came.
E)
At least two of the above are incorrect.
81. Which of the following molecules or ions is not paramagnetic in its ground state?
A)
O2
B)
O2+
C)
B2
D)
NO
E)
F2
82. Which of the following electron distributions among the molecular orbitals best describes
the NO molecule?
2s
2s*
2py=2px
2pz
2py*=2px*
2pz*
A)
2 2 4 2 4 2
B)
2 2 4 2 4 1
C)
2 2 4 1 3 0
D)
2 2 4 2 2 0
E)
2 2 4 2 1 0
83. Consider the molecular orbital energy level diagrams for O2 and NO. Which of the
following is true?
I.
Both molecules are paramagnetic.
II.
The bond strength of O2 is greater than the bond strength of NO.
III.
NO is an example of a homonuclear diatomic molecule.
IV.
The ionization energy of NO is smaller than the ionization energy of NO+.
A)
I only
B)
I and II
C)
I and IV
D)
II and III
E)
I, II, and IV
84. In the molecular orbital description of CO:
A)
The highest energy electrons occupy antibonding orbitals.
B)
Six molecular orbitals contain electrons.
C)
There are two unpaired electrons.
D)
The bond order is 3.
E)
All of the above are false.
85. Consider the molecular orbital description of the NO– anion. Which of the following
statements is false?
A)
NO– is paramagnetic.
B)
NO– is isoelectronic with CO.
C)
The bond energy in NO+ is greater than the bond energy in NO–.
D)
The bond order in NO– is 2.
E)
Statements A through D are false.
86. Which of the following has the greatest bond strength?
A)
B2
B)
O2–
C)
CN–
D)
O2+
E)
NO–
87. The bond order in the NO molecule is
A)
1
B)
C)
2
D)
E)
3
88. The CO molecule has the bond order:
A)
0
B)
1
C)
2
D)
3
E)
4
89. The bond order for CN– is 2.
90. Which of the following statements about the CO32– ion is false?
A)
The orbitals on the carbon atom are sp2 hybridized.
B)
The ion is expected to be diamagnetic.
C)
The C–O bonds are different lengths.
D)
The ion has a total of 24 electrons.
E)
All the above statements are true.
91. The following statements concern molecules that require resonance. Which is true?
A)
The pi bonding is most clearly delocalized.
B)
The sigma bonding is most clearly delocalized.
C)
Both the sigma and pi bonding are delocalized.
D)
The benzene molecule is best described by the MO theory.
E)
The benzene molecule is best described by the localized electron model.
92. Sulfur trioxide is known to be planar with all the oxygen atoms equidistant from the central
sulfur atom. On the basis of these facts, which of the following conclusions may be drawn
concerning this molecule?
I. It can be represented by three equivalent resonance structures.
II. The dipoles associated with each S–O bond are equal in magnitude.
III. The sulfur atom is sp2 hybridized.
A)
I only
B)
II only
C)
III only
D)
I and II only
E)
I, II, and III
93. How many electrons are involved in pi bonding in benzene, C6H6?
A)
12
B)
30
C)
3
D)
6
E)
18
94. Which of these statements about benzene is true?
A)
All carbon atoms in benzene are sp3 hybridized.
B)
Benzene contains only bonds between C atoms.
C)
The bond order of each C–C bond in benzene is 1.5.
D)
Benzene is an example of a molecule that displays ionic bonding.
E)
All of these statements are false.
95. Consider the benzene molecule. Which of the following statements about the molecule is
false?
A)
All six C–C bonds are known to be equivalent.
B)
Each carbon atom is sp2 hybridized.
C)
The localized electron model must invoke resonance to account for the six equal
C–C bonds.
D)
It has delocalized pi bonding in the molecule.
E)
The pi bonds of carbon involve sp2 orbitals.
96. The C–C–H bond angles in ethylene, C2H4, are 120°. What is the hybridization of the
carbon orbitals?
97. The mixing of native atomic orbitals to form special orbitals for bonding is called
__________.
98. Consider three molecules – A, B, C. Molecule A has a hybridization of sp3. Molecule B has
two more effective pairs (electron pairs around the central atom) than molecule A. Molecule
C consists of one bond and two bonds. Give the molecular structure, hybridization, bond
angles, and an example for each molecule.
99. Consider the structure of glycine, the simplest amino acid:
a) Indicate the hybridizations at each N and C atom in the molecule.
b) What is the total number of bonds in the molecule?
c) What is the total number of bonds in the molecule?
100. A(n) __________ molecular orbital is lower in energy than the atomic orbital of which it is
composed.
101. The number of molecular orbitals formed is always __________ the number of atomic
orbitals combined.
102. __________ is the difference between the number of bonding electrons and the number of
antibonding electrons divided by two.
103. __________ causes a substance to be attracted into the inducing magnetic field.
104. Draw a molecular orbital diagram for O2 and N2. Using molecular orbital theory, explain
why the removal of one electron in O2 strengthens bonding, while the removal of one
electron in N2 weakens bonding.
See Sec. 9.3 of Zumdahl, Chemistry
105. Give the bond order for each of the following:
a)
H2
b)
H2+
c)
H2–
d)
CN–
e)
CN
f)
CN+
106. Which of the following are paramagnetic?
O2 O2– O22– B2 C2 N2 F2 CN– P2
107. The concept of __________ is required for certain molecules because the localized electron
model assumes electrons are located between a given pair of atoms in a molecule.
108. Explain the concept of delocalization of electrons in SO3. Indicate how this idea relates to
resonance.
