Chemistry 111 Sect. 3
Exam #3
November 30, 2000
Name: ________________________________________________
Student #: ________________________________________________
Please put your name and student number on all pages in case they become separated. The
last page of the exam has some useful information. The exam lasts 60 minutes. There are a
total of 100 points.
MULTIPLE CHOICE QUESTIONS
Place an X in the box corresponding to the correct answer.
1. (5 pts) Arrange the following neutral elements in order of increasing atomic radius.
Cl, Cs, Si, Sn, Sr
smallest → largest
o
Cs < Sr < Sn < Si < Cl
o
Cl < Si < Sn < Sr < Cs
o
Cl < Cs < Si < Sn < Sr
o
Sr < Sn < Si < Cs < Cl
o
Si < Cl < Sr < Sn < Cs
2. (7 pts) According to the octet rule, the carbon-oxygen bond in the molecule COBr2, in which
carbon is bonded to O and Br atoms, is a:
o
single bond
o
o
o
o
double bond
triple bond
quadruple bond
resonance bond
3. (8 pts) In principle, dinitrogen monoxide, N2O or N≡N–O, can decompose to nitrogen and
oxygen gas:
2 N2O (g) → 2 N2 (g) + O2 (g)
Estimate the enthalpy change for this reaction in kJ from the bond energies on p. 6.
o
o
o
o
o
-297
-96
96
716
4680
Page 1
Chemistry 111 Sect. 3
Name: ________________________________________________
Exam #3
Student #: ________________________________________________
November 30, 2000
4. (5 pts) The bond angle a shown below for the molecule acetonitrile is, in degrees:
o
o
o
o
o
45
a
90
109.5
H
H C
120
C
N:
H
180
5. (5 pts) The element potassium (K) has a ________ first ionization energy and a ________
electronegativity than the element fluorine (F).
o
o
o
o
o
higher, higher
higher, lower
lower, higher
lower, lower
equal, equal
6. (7 pts) The electron pair geometry around the central atom in H2O is:
o
o
o
o
o
linear
trigonal planar
tetrahedral
trigonal bipyramidal
octahedral
7. (8 pts) The bond order for a carbon – oxygen bond in carbonate ion (Lewis structure
shown below) is:
o
o
o
o
o
1
1.33
2
2-
:O:
3
4
.. C
:O
..
MULTIPLE MULTIPLE CHOICE QUESTIONS
Page 2
..
O:
..
Chemistry 111 Sect. 3
Name: ________________________________________________
Exam #3
Student #: ________________________________________________
November 30, 2000
Place an X in the boxes corresponding to the correct answers. Any number of answers may
be correct, including none of them.
8. (10 pts) For which of the labeled atoms in sulfuric acid, H2SO4 shown below, is the formal charge
equal to zero?
o
H1
o
O2
o
O3
o
O4
o
S5
4
..
:O: 5
..
..
S
H O
O
..
..
:O:
1 2
..
3
9. (10 pts) Which of the following are true?
o
Resonance Lewis structures always include a double or triple bond.
o
The electronic geometry of a molecule is always the same as its molecular geometry.
o
A fluoride ion has a smaller radius than a fluorine atom.
o
An N≡C bond is shorter than an N–C bond.
o
The polarity of a molecule depends only on its geometry.
10. (5 pts) Which of the following molecules is NOT polar?
o
CCl4
o
H2O
o
Cl2
o
HCl
o
NH3
SHORT ANSWER QUESTIONS
Answer in the spaces indicated.
Page 3
H
Chemistry 111 Sect. 3
Exam #3
November 30, 2000
Name: ________________________________________________
Student #: ________________________________________________
11. (7 pts) Draw the Lewis structure for SO3.
12. (8 pts) Draw the Lewis structure for SF4.
13. (7 pts) The Lewis structure for PCl3 is given below. What is the molecular geometry of
PCl3?
..
:Cl
..
..
:Cl:
P:
:Cl:
..
14. (8 pts) The Lewis structure for SF6 is given below. What is the molecular geometry of
SF6?
..
.. :F:
:F
..
S
..
:F
.. :F:
..
..
F:
..
..
F:
..
Page 4
Chemistry 111 Sect. 3
Exam #3
November 30, 2000
Name: ________________________________________________
Student #: ________________________________________________
Useful information
c = 3.0 × 108 m/sec
h = 6.6 × 10-34 J sec
Rhc = 2.2 × 10-18 J
me = 9.1 × 10-28 g
a0 = 0.0529 nm
NA = 6.02 × 1023 molecules/mol
2-linear, 3-trigonal planar, 4-tetrahedral
5-trigonal bipyramidal, 6-octahedral
∆Hrxn = Σ(bond ener)react - Σ(bond ener)prod
q = C m ∆T
Bond
H-C
H-H
H-N
H-O
C-C
q = (heat of fusion) m
∆H = qp
∆H0net = Σ (∆H0f)prod - Σ (∆H0f)react
∆H0net = Σ (∆H0rxn)
c = λν
E = hν
E = -Rhc/n2
λ = h/(m v)
Z* = Z - ninner electons
d = m/V
Some useful data
Bond Bond
Bond
energy
(kJ/mol)
C-N
305
C=C
C-O
358
C≡C
N-N
163
C=N
N-O
201
C≡N
O-O
146
C=O
Bond
energy
(kJ/mol)
413
436
391
463
346
Bond
energy
(kJ/mol)
602
835
615
887
732
Bond
Bond
energy
(kJ/mol)
1072
418
945
607
498
C≡O
N=N
N≡N
N=O
O=O
PERIODIC TABLE OF THE ELEMENTS
IA
IIA
IIIB
IVB
VB
VIB
VIIB
VIIIB
IB
IIB
IIIA
IVA
VA
VIA
VIIA VIIIA
1
2
H
He
1.008
4.003
3
4
5
6
7
8
9
Li
Be
B
C
N
O
F
10
Ne
6.939
9.012
10.81
12.01
14.01
16.00
19.00
20.18
11
12
13
14
15
16
17
18
Na
Mg
Al
Si
P
S
Cl
Ar
22.99
24.31
19
20
21
22
K
Ca
Sc
Ti
39.10
40.08
44.96
37
38
39
Rb
Sr
85.47
55
26.98
28.09
30.97
32.07
35.45
39.95
24
25
26
27
28
29
30
31
32
33
34
35
36
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
47.90
50.94
52.00
54.94
55.85
58.93
58.71
63.55
65.39
69.72
72.61
74.92
78.96
79.90
83.80
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
87.62
88.91
91.22
92.91
95.94
(99)
101.1
102.9
106.4
107.9
112.4
114.8
118.7
121.8
127.6
126.9
131.3
56
57
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
Cs
Ba
La
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
132.9
137.3
138.9
178.5
181.0
183.8
186.2
190.2
192.2
195.1
197.0
200.6
204.4
207.2
209.0
(209)
(210)
(222)
87
88
89
Fr
Ra
Ac
(223)
226.0
227.0
23
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I
Xe
Chemistry 111 Sect. 3
Exam #3
November 30, 2000
Name: ________________________________________________
Student #: ________________________________________________
Page 6