CHEM 200/202
Exam 3-A
CHEM _______
Lab Section Number: _____
November 15, 2014
Name (printed):_____________________________________________
(Last)
(First)
Signature:______________________________________
This exam consists of 32 questions at 5 points each for a total of 160 points.
Make sure that your test has all of the pages. Please read each problem
carefully. There are no intentionally misleading questions; each problem
should be taken at its face value. Please mark your answers on the Scantron
sheet provided to you and on the actual exam.
You will be given a periodic table and an exam information sheet to use
during the exam. You may remove it from the exam make it more accessible.
You may also use the designated Casio fx-300ms-plus calculator or
equivalent non-programmable non-graphing scientific calculator during the
exam. Use the back pages of the test as scratch paper. You are not allowed to
use any devices capable of accessing the internet, textbooks, notes, or
homemade reference sheets during the exam.
You may leave if you finish the exam early. Give the exam and the
information sheet to your TA and leave quietly without disturbing other
students. Before leaving, check that all your answers have been properly
entered on the Scantron sheet and the exam and that your name is written on
every page of the exam and on the Scantron sheet.
All cell phones and electronic devices must be turned off and put away.
Please remove all hats and caps. Place your books and all papers out of sight
under your seat. If the TA believes that you might be looking at your
neighbor’s paper, you will be asked to move to a new location.
Exam scores will be posted on Blackboard as soon as the grading is
complete. Your test will be returned to you in the first lab meeting of next
week. If you have any questions regarding the grading of your exam, please
notify your TA.
The time available for the exam is 120 minutes. Good luck!
CHEM 200/202
Exam 3-A
Name: ___________________________________________
November 15, 2014
Lab Section #: _______
Please mark your answers on the scantron sheet using a #2 pencil and also mark your answers
on the exam itself.
Mark Test From “A” on your scantron.
1. Which of the following is an ionic compound? a) KI
b) NH3
c) I2
d) H2S
e) CCl4
2. Of these substances, in which are the atoms held together by metallic bonding? a) CO2(g)
b) Si(s)
c) Br2(l)
d) S8(s)
e) Cr(s)
3. Which statement below best describes the location of the electrons involved in a covalent
bond?
a) The electrons are delocalized evenly, everywhere, between all the atoms in the
substance.
b) The electrons have a higher probability of being found directly between adjacent
nuclei.
c) The electrons form a straight line bridging the adjacent nuclei.
d) The electrons are removed from one atom and found exclusive around the adjacent
atom.
e) The electrons are on the far sides of the nuclei, which touch to form a covalent bond.
4. What is the molecular formula of the ionic compound formed by barium and nitrogen?
a) BaN
b) BaN2
c) Ba2N3
d) Ba2N
e) Ba3N2
5. The lattice energy for ionic crystals increases as the charge on the ions _____________
and the size of the ions __________________. a) increases, increases
b) increases, decreases
c) decreases, increases
d) decreases, decreases
e) None of these choices is generally correct.
Page 1 of 9
CHEM 200/202
Exam 3-A
November 15, 2014
6. Calculate the lattice energy of magnesium sulfide from the data given below.
Mg(s) → Mg(g)
∆H° = 148 kJ/mol 2+
Mg(g) → Mg (g) + 2e¯
∆H° = 2186 kJ/mol
S8(s) → 8S(g)
∆H° = 2232 kJ/mol
S(g) + 2e¯ → S2¯(g)
∆H° = 450 kJ/mol
8Mg(s) + S8(s) → 8MgS(s)
∆H° = -2744 kJ/mol
MgS(s) → Mg2+(g) + S2¯(g)
∆H°lattice = ? a)
b)
c)
d)
e)
-3406 kJ/mol
-2720. kJ/mol
2720. kJ/mol
3406 kJ/mol
None of these choices are correct.
7. The diameter of a chloride ion is 362 pm, and the diameter of a potassium ion is 276 pm.
What is the distance between the nuclei of adjacent chloride and potassium ions in solid
potassium chloride? a) 1276 pm
b) 638 pm
c) 319 pm
d) 181 pm
e) 138 pm
8. Select the element whose Lewis symbol is correctly represented.
A
D
E
• Ra •
• Pb •
Te
He•
••
Fr •
C
••
•
B
9. The melting point of MgO is 2852°C, whereas SO2 has a melting point of -97.6°C. If quartz
(SiO2) is a solid with a melting point of 1550°C, the bonding in quartz is best described as:
a) lattice energy
b) network attractions
c) ionic bonding
d) network covalent bonding
e) metallic bonding
••
••
••
10. Which of the atoms listed below is the most electronegative?
a) Rb
b) Li
c) As
d) Al
e) N
•
Page 2 of 9
CHEM 200/202
Exam 3-A
November 15, 2014
11. The reaction between methane and chlorine gas is exothermic and produces carbon
tetrachloride and hydrogen chloride gasses. Given the reaction, its enthalpy, and the
respective bond energies, determine the bond energy of the Cl Cl bond.
CH4(g) + 4Cl2(g) → 4HCl(g) + CCl4(g) ∆H°rxn = -440 kJ
Bond energies:
C H = 413 kJ/mol; C Cl = 339 kJ/mol; C C = 347 kJ/mol; H Cl = 427 kJ/mol
a) 60.8 kJ/mol
b) 330 kJ/mol
c) 243 kJ/mol
d) 972 kJ/mol
e) 156 kJ/mol
••
N
••
Cl
••
C
••
••
D
••
••
D
•• •• •• ••
••
•• ••
••
C Cl N C
N
••
••
•• ••
••
••
••
••
••
••
••
••
••
••
••
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O
••
O
••
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••
••
••
I
••
E
1-
••
••
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O
I
O
••
••
••
O
••
O
••
Page 3 of 9
••
••
••
••
O
••
O
••
••
••
O
••
O
••
O
I
O
••
••
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I
O
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1-
O
••
••
O
••
O
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I
••
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••
O
E
1-
O
••
O
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I
D
1-
O
••
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••
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O
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O
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O
C
1-
••
••
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O
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1-
O
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D
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B
O
••
N
••
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A
I
N
1-
O
••
••
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C
I
O
••
••
15. Select the Lewis structure in which the formal charges on the atoms in periodate
(IO4 )O
are
best minimized.
O
O
••
E
••
14. Which ••
of the••molecules
below is not
an example
••
••
•• of an expanded octet?
2
C
N
C
N
••
Cl
a) Cl
SO
4
••
••
••
b) ClO3
c) XeF4
d) PCl3
e) PO43 ••
••
E
••
C Cl
•• N C
••
Cl
•• ••
C
Cl N C
•• ••
••
E
••
C
•• ••
N
Cl
••
••
••
••
C
••
••
••
••
••
••
Cl
••
••
••
••
N
••
••
Cl
N
••
••
••
CCl
NC
••
••
C
D
C
••
••
Cl
••
B
••
A
••
Cl
N
••
C
••
••
CCl
NC
••
B
••
••
Cl
••
B
••
13. Select the best Lewis structure for ClCN.
A
••
A
••
12. Which is the strongest bond of those listed below?
a) H Cl
b) H F
c) H Br
d) H At
e) H I
•
O
•
F
••
F
D
E
••
••
F
••
••
••
••
F
••
••
••
•F•
Br
Br
••
••
••
••
F
••
•F•
F
F
••
Br
••
••
••
••
••
••
••
••
Br
••
••
•F•
••
••
••
F
F
••
••
••
••
•F•
••
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••
E
••
••
••
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F
D
F
Br
F
••
••
F
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••
C
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••
••
B
••
••
F
••
••
••
••
••
••
F
••
••
••
••
B
••
••
A
Br
••
••
••
••
16. Which is the proper representation of bromine trifluoride?
•F•
••
••
November
15, 2014 •F•
F
••
B
C
••
••
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B
••
••
F
••
F
••
Exam 3-A••
••
••
CHEM 200/202
••
••
A
F
••
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F
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O
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N
O
••
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O
••
H
••
•• atom in nitric acid (HNO3)?
17. What is the formal charge of the nitrogen
F
••
••
a) -2 F
Br
Br
••
b) -1 ••
F
••
••
c) 0
•F•
d) +1
e) +2
18. Which molecule below does not have a resonance structure?
a) O3
b) ClO4
c) PO43
d) CO2
e) SO32 19. Of the bond angles listed below, which is not a bond angle between chlorine atoms,
predicted by the VSEPR structure, on PCl5?
a) 90°
b) 109.5°
c) 120°
d) 180°
e) All these bond angles are found in PCl5.
20. Which of the molecules listed below has a square planar structure?
a) NH4+
b) XeF4
c) SO42
d) XeO2F2
e) IF4+
21. Which one of the molecules below is not correctly paired with its predicted VSEPR
structure?
a) SO42 : tetrahedral
b) IF4+ : see-saw
c) CO32 : trigonal planar
d) H2O : linear
e) SF6 : octahedral
Page 4 of 9
CHEM 200/202
Exam 3-A
November 15, 2014
22. Which one of the molecules listed below does not have a central atom with sp3
hybridization?
a) BCl3
b) NH3
c) H3O+
d) PCl3
e) CH4
23. What is the hybridization of the carbon atom in thiocyanate (SCN )?
a) sp
b) sp2
c) sp3
d) sp3d
e) The carbon atom is not hybridized
24. Which of the following will result in the least, or no, disruption to the ideal bond angles
around a central atom?
a) A lone pair of electrons.
b) A double bond to oxygen.
c) A double bond to sulfur.
d) A single bond to hydrogen.
e) Nothing disrupts bond angles.
25. Which one of the molecules below exhibits molecular polarity?
a) NH4+
b) CO2
c) SO42
d) OCN
e) BF3
26. Which statement pertaining to sigma bonds is incorrect?
a) Methane (CH4) contains four sigma bonds.
b) Sigma bonds have very high electron density along the axis of the bond.
c) Sigma bonds form from the direct overlap of any two orbitals on adjacent atoms.
d) All bonds between atoms contain sigma bonds.
e) Double bonds are the result of a pair of sigma bonds between the same two atoms.
27. How many sigma and pi bonds are there in a molecule of SO3?
a) Three sigma bonds and zero pi bonds.
b) Two sigma bonds and one pi bond.
c) One sigma bond and two pi bonds.
d) Three sigma bonds and three pi bonds.
e) Four sigma bonds and two pi bonds.
Page 5 of 9
CHEM 200/202
Exam 3-A
November 15, 2014
Use the molecular orbital diagram below to assist in answering the next three questions.
28. Using the MO diagram, determine the bond order for the BN (boronitride) molecule?
a) 0
b) 1
c) 1.5
d) 2
e) 3
30. How many electrons does the diatomic ion N2
have in anti-bonding molecular orbitals?
a) 0
b) 1
c) 2
d) 3
e) 4
Energy
29. Which one of the following diatomic molecules is
paramagenetic?
a) N2
b) CN
c) BN
d) C2
e) B2
Page 6 of 9
CHEM 200/202
Exam 3-A
November 15, 2014
The following problems are extra credit. You will not be penalized for wrong answers.
31. What is the hybridization of the iodine atom in IF4+?
a) sp
b) sp2
c) sp3
d) sp3d
e) sp3d2
32. In the figure below the curved line represents the potential energy of the bond in a molecule
of H2. Which point on the figure (represented by the letters) shows the optimal length of the
H H bond?
Potential Energy (kJ/mol)
A
0
E
-150
D
B
-300
C
-450
100
200
Internuclear Distance (pm)
Page 7 of 9
CHEM 200/202
Exam 3-A
November 15, 2014
This Page Left Blank For Calculations
Page 8 of 9
CHEM 200/202
Exam 3-A
November 15, 2014
This Page Left Blank For Calculations
Page 9 of 9
San Diego State University |
CHEM 200 Exam/Quiz Information Sheet – Fall 2013
Physical Quantities
atomic mass unit (amu) = 1.66056 x 10-27 kg
Avogadro’s number = 6.022 x 1023
universal gas constant (R) = 8.314 J/K mol = 0.08206 L atm/K mol
absolute zero = -273.15 ˚C = 0 K
specific heat capacity of water (cH2O) = 4.184 J/g K
speed of light (c) = 3.000 x 108 m/s
Planck’s constant (h) = 6.626 x 10-34 J s
Conversion Factors
1 angstrom (Å) = 10-10 m
1 atm = 1.01325 x 105 Pa = 1.01325 bar = 760 Torr
1 calorie = 4.184 J
1 joule = 1 kg m2/s2
Equations
PV = nRT
PA = XA Ptotal
d=
(molar mass)
RT
urms =
P
3RT
molar mass
E=q+w
Hrxn =
H°f(products) -
H°f(reactants)
heat capacity = q/ T
specific heat capacity (c) = q/(mass
speed of light (c) =
T)
x
hc
Ephoton = h =
2
Eelectron = -2.18 x 10-18 J ( Z2 )
n
h
=
mu
1 = 1.096776 x 107 m-1 ( 1 – 1 ), where n > n
2
1
n21 n22
13
Periodic Table of the Elements
1
1
18
1
2
H
1.008
2
3
4
5
6
7
3
2
13
14
15
16
17
4
5
6
7
8
9
He
4.003
10
Li
Be
B
C
N
O
F
Ne
6.941
9.012
10.81
12.01
14.01
16.00
19.00
20.18
11
12
Na
Mg
22.99
24.31
19
13
3
20
21
4
22
5
23
6
24
7
25
8
26
9
27
10
28
11
29
12
30
14
15
16
17
18
Al
Si
P
S
Cl
Ar
26.98
28.09
30.97
32.07
35.45
39.95
31
32
33
34
35
36
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
39.10
40.08
44.96
47.87
50.94
52.00
54.94
55.85
58.93
58.69
63.55
65.39
69.72
72.64
74.92
78.96
79.90
83.80
Rb
37
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
52
53
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
38
56
Cs
Ba
132.9
137.3
87
88
Fr
Ra
[223]
[226]
*
Lanthanoids
**
Actinoids
39
57-70
*
89-102
**
57
71
40
72
41
73
42
74
43
75
44
76
45
77
46
78
47
79
48
80
48
81
50
82
51
83
84
85
54
86
Lu
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
175.0
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]
[220]
Metals
Non
Metals
103
104
105
106
107
108
109
Lr
Rf
Db
Sg
Bh
Hs
Mt
[262]
[261]
[262]
[266]
[264]
[277]
[268]
58
59
60
61
62
63
64
65
66
67
68
69
70
La
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
138.9
140.1
140.9
144.2
[145]
150.4
152.0
157.3
158.9
162.5
164.9
167.3
168.9
173.0
89
90
91
92
93
94
95
96
97
98
99
100
101
102
[243]
[247]
Ac
Th
Pa
U
Np
Pu
[227]
232.0
231.0
238.0
[237]
[244]
Am Cm
Bk
Cf
Es
Fm
Md
No
[247]
[251]
[252]
[257]
[258]
[259]
© 2008 San Diego State University, Department of Chemistry