CHEM 1314 3;30 pm Theory
Exam !IV
John IV. Gelder
December 9, 2003
Name ________________________
TA's Name ________________________
Lab Section
______________________
INSTRUCTIONS:
1. This examination consists of a total of 7 different pages.
The last page includes a periodic table and some useful
equations. All work should be done in this booklet.
2. PRINT your name, TA's name and your lab section
number now in the space at the top of this sheet. DO
NOT SEPARATE THESE PAGES.
3. Answer all questions that you can and whenever called
for show your work clearly. Your method of solving
problems should pattern the approach used in lecture.
4. No credit will be awarded if your work is not shown in
problems 5, 6a, and 6b.
5. Point values are shown next to the problem number.
6. Budget your time for each of the questions. Some
problems may have a low point value yet be very
challenging. If you do not recognize the solution to a
question quickly, skip it, and return to the question after
completing the easier problems.
7. Look through the exam before beginning; plan your
work; then begin.
8. Relax and do well.
SCORES
Page 2
Page 3
Page 4
Page 5
Page 6
TOTAL
_____
(22)
_____
(33)
_____
(21)
_____
(16)
_____
(15)
______
(100)
CHEM 1314 EXAM IV
PAGE 2
(14) 1a. Draw Lewis structure(s) for the following ion. If resonance hybrids exist include each possible form.
i)
HCO3–
b)
What is the bond order of each C-O bond in HCO3–? (Note: Be sure to clearly label your assignment .)
(3)
C-O1 bond order 1.5
C-O2 bond order 1.5
C-O3 bond order 1
c)
How many sigma(s) and how many pi(p) bonds are in the ion? (2)
4 sigma bonds and 1 pi bond.
d)
Using terms localized and delocalized describe the sigma and pi bonds in this ion. (5)
The 4 sigma bonds are localized. The pi electrons are delocalized over C, O1 and O2
(8)
2. Indicate the atomic or hybrid orbitals on each atom in the following molecules that are involved in
forming the covalent bond(s).
a)
H2CO
C(sp2 ) – O(2p)
C(sp2 ) – H(1s) for both C-H bonds
b)
ClO2Cl(sp3 ) – O(2p)
for bond Cl-O bonds
CHEM 1314 EXAM IV
PAGE 3
(22) 3. Complete the following table. Omit grayed cells.
(11)
Formula
# bonding
Groups (CA)
# lone pairs of
electrons (CA)
Molecular
Geometry
Bond
Angle(s)
Polar or
Nonpolar
Hybridization
(CA)
O3
2
1
Bent
~120˚
Polar
sp2
XeF4
4
2
Square
planae
ClOF2
+
3
1
Trigonal
pyramid
al
CCl2F2
4
0
Tetrahedral
180˚ and Nonpolar
90˚
Less
than
109˚
~109˚
sp3
Polar
sp3
4. Below is figure showing a Lewis structure model for an amino acid.
a) What is the hybridization around C(1), S, C(2), C(4), N and C(6)?
Atom
C(1)
S
C(2)
C(4)
N
C(6)
Hybridization
sp3
sp3
sp3
sp3
sp3
sp2
b) What are the bond angles for each of the following sets of atoms? C(1)-S-C(2), N-C(4)-C(6), C(4)C(6)O(5), C(6)-O(5)-H, H-C(3)-H.
Atoms
C(1)-S-C(2)
N-C(4)-C(6)
C(4)C(6)-O(5)
C(6)-O(5)-H
H-C(3)-H
Bond Angle
~109˚
~109˚
~120˚
~109˚
~109˚
CHEM 1314 EXAM IV
PAGE 4
(21) 5a. A container of constant volume has 0.456 mol of methane, CH4, at 670. mmHg and 30.0 ˚C. If the
temperature is held constant, calculate the new pressure if 0.311 mol of methane are added to the
container. (7)
P2 = 1127 mm Hg
b) Calculate the volume of the container used in part a). (7)
V = 12.9 L
c) Calculate the density of methane at STP. (7)
Density = 0.713 g L- 1
CHEM 1314 EXAM IV
PAGE 5
(16) 6. The compound dichlorodifluoromethane, CF2Cl2, can be recycled into another compound by reacting
with hydrogen gas as described in the chemical equation below,
CF2Cl2(g) + 2H2(g) Æ CH2F2(g) + 2HCl(g)
a) A mixture of hydrogen and dichlorodifluoromethane is prepared in a 20.0 L container at 100. ˚C. The
partial pressure of hydrogen in the container is 6.47 atm. Calculate the partial pressure of
dichlorodifluoromethane in the container that will react with all of the hydrogen. (10)
PCF2 Cl2 = 3.24 atm
b) What is the total pressure in the 20.0 liter container before the reaction begins? (3)
PT = 9.71 atm
c) During the reaction between the hydrogen and the dichlorodifluoromethane would you expect the total
pressure to increase, decrease or remain constant? Explain. NOTE: Assume the temperature and the
volume of the container remain constant during the reaction? (3)
Stay the same. The number of moles of products (using coefficients) in the gas phase equal the
number of moles of reactants (using coefficients) in the gas phase.
CHEM 1314 EXAM IV
(8)
PAGE 6
7. Explain, in terms of the kinetic molecular model, why increasing the temperature of a sample of a fixed
amount of an ideal gas increases the pressure of the gas at constant volume.
Increasing the temperature increases the velocity of the gas particles so the particles hit the
walls of the container more frequently and with greater force….increasing the pressure.
CHEM 1314 EXAM IV
Periodic Table of the Elements
IA
1
1
PAGE 7
VIIIA
2
H
He
1.008 IIA
3
4
IIIA IVA VA VIA VIIA 4.00
5
Li Be
2
6.94 9.01
11
12
3
4
5
6
7
6
B
7
8
9
10
C
N
O
F Ne
Al Si
P
S
Cl Ar
10.81 12.01 14.01 16.00 19.00 20.18
13
14
15
16
17
18
Na Mg
22.99 24.30 IIIB IVB VB VIB VIIB
19
20
21
22
23
24
25
26
K Ca Sc Ti
VIII
27
IB
28
29
IIB 26.98 28.09 30.97 32.06 35.45 39.95
30
31
32
33
34
35
36
V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
39.10 40.08 44.96 47.88 50.94 52.00 54.94 55.85 58.93 58.69 63.55 65.38 69.72 72.59 74.92 78.96 79.90 83.80
37
38
39
40
41
42
43 44
45
46
47
48
49
50
51
52
53
54
Rb Sr
Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te
I
Xe
85.47 87.62 88.91 91.22 92.91 95.94 (98) 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3
55
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
132.9 137.3 138.9 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 (209) (210) (222)
87
88
89
104 105 106 107 108 109 110 111 112
114
116
Fr Ra Ac Rf Db Sg Bh Hs Mt
(223) 226.0 227.0 (261) (262) (266) (264) (269) (268) (271) (272) (277)
Lanthanides
Actinides
58
59
60
61
62
63
64
65
(285)
66
67
(289)
68
69
70
71
Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu
140.1 140.9 144.2 (145) 150.4 152.0 157.2 158.9 162.5 164.9 167.3 168.9 173.0 175.0
90
91
92
93
94
95
96
97
98
99
100 101 102 103
Th Pa U
Np Pu Am Cm Bk Cf Es Fm Md No Lr
232.0 231.0 238.0 237.0 (244) (243) (247) (247) (251) (252) (257) (258) (259) (260)
Useful Information
L. atm
mol. K
1 atm = 760 mm Hg
R = 0.08203
u=
r1
r2 =
PV = nRT
3RT
MM
MM2
MM1
Avogadro's number = 6.02 x 1023
g
density of water = 1.00 mL
K = ˚C + 273.15