Last Name: _____________________________ First Name: _______________
Lab Sec. # ____
TA: ____________________ Lab day/time: _____________
Dr. Enderle
CHEMISTRY 2A (A)
Final Exam – Fall 2009
Instructions:
CLOSED BOOK EXAM! Do not open the exam until instructed to do so. No
books, notes, or additional scrap paper are permitted. All information required
is contained on the exam. Place all work in the space provided. If you require
additional space, use the back of the exam. A scientific calculator may be used
(if it is a programmable calculator, its memory must be cleared before the
exam). Sharing of calculators is not allowed.
(1)
(2)
(3)
(4)
(5)
Read each question carefully.
Answer all the questions you are sure of first, and then use the remaining
time for the rest.
Please show all relevant work where it is indicated for full credit.
The last 2 pages contain a periodic table and some useful information.
You may remove them for easy access and for scratch.
If you finish early, recheck your answers.
UC Davis is an Honor Institution
Possible Points
Points
# 1-20
(3 points each)
/ 60
# 21-22
(16 points)
/ 16
# 23
(54 points)
/ 54
# 24-25
(21 points)
/ 21
# 26-27
(11 points)
/ 11
# 28
(15 points)
/ 15
# 29
(14 points)
/ 14
# 30
(11 points)
/ 11
# 31
(11 points)
/ 11
Total Score (213)
/ 213
Multiple Choice
Circle one
1.
a b
c d
e
2.
a b
c d
e
3.
a b
c d
e
4.
a b
c d
e
5.
a b
c d
e
6.
a b
c d
e
7.
a b
c d
e
8.
a b
c d
e
9.
a b
c d
e
10. a b
c d
e
11. a b
c d
e
12. a b
c d
e
13. a b
c d
e
14. a b
c d
e
15. a b
c d
e
16. a b
c d
e
17. a b
c d
e
18. a b
c d
e
19. a b
c d
e
20. a b
c d
e
Fall 2009
FINAL CHEM 2A
(Page 2 of 13)
Concepts: Multiple Choice
Questions 1-13: 3 points each (no partial credit)
1. How many hydrogen atoms are represented in the formula Fe(C5H7O2)3?
(A) 3
(B) 7
(C) 14
(D) 21
(E) 42
2. The formula of potassium sulfate is K2SO4. The formula of iron(III) chloride is FeCl3. What is the
formula of iron(III) sulfate?
(A) Fe2(SO4)3
(B) Fe(SO4)2
(C) Fe2SO4
(D) Fe3(SO4)2
(E) Fe3SO4
3. Which substance is not a gas at room temperature and atmospheric pressure?
(A) Ar
(B) CH4
(C) N2
(D) CO2
(E) K
4. A 1.0 g sample of oxygen gas occupies a fixed-volume container at a pressure of 0.50 atm. If the
temperature is increased, then
(A) the density of the oxygen gas will decrease.
(B) the density of the oxygen gas will increase.
(C) the speed of the oxygen molecules will decrease.
(D) the pressure of the oxygen gas will increase.
(E) the pressure of the oxygen gas will decrease.
5. The average kinetic energy of the molecules of an ideal gas is proportional to its
(A) temperature. (B) volume. (C) density. (D) pressure. (E) amount in moles.
6. When the chemical equation
NH3(g)
+
O2(g)
→
NO2(g)
+
H2O(g)
is balanced, what is the smallest integer for the coefficient of O2(g)?
(A) 3
(B) 9
(C) 5
(D) 7
(E) 1
7. In a chemical reaction, which of the following cannot change between reactants and products?
(A) total mass (B) total moles (C) volume (D) pressure (E) temperature
8. Which species has the Lewis symbol
(A) Si
(B) N
(C) Cl
9. Which bond is most polar?
(A) H–O
(B) N–O
(C) F–F
Z
?
(D) O
(E) Ca2+
(D) H–C
(E) C–N
10. Which of the following represents a neutralization reaction of an acid with a base?
(A) 2 H2(g) + O2(g) → 2 H2O(l)
(B) NH4OH(aq) + HCl(aq) → NH4Cl(aq) + H2O(l)
(C) 2 NaOH(aq) + CuCl2(aq) → 2 NaCl(aq) + Cu(OH)2(s)
(D) HBr(aq) + AgNO3(aq) → HNO3(aq) + AgBr(s)
(E) 2 H2O2(aq) → 2 H2O(l) + O2(g)
Fall 2009
FINAL CHEM 2A
(Page 3 of 13)
11. The balanced chemical equation
2 HCl(aq) + CO32- (aq) → 2 Cl-(aq)+ H2CO3(aq)
(A) involves the oxidation of C.
(B) involves the reduction of C.
(C) involves an acid and a base.
(D) involves a change in oxidation numbers.
(E) is an example of a combustion reaction.
12. What is the number of neutrons, protons, and electrons in the species 37Cl- ?
(A) 20 neutrons, 17 protons, and 18 electrons
(B) 18 neutrons, 17 protons, and 20 electrons
(C) 37 neutrons, 17 protons, and 17 electrons
(D) 17 neutrons, 20 protons, and 18 electrons
(E) 17 neutrons, 17 protons, and 19 electrons
13. The electronic configuration of P is
(A) 1s22s22p3 (B) 1s22s22p11 (C) 1s22s22p63s23p3
(D) 1s22s22p63p5 (E) 1s22s22p62d5
14. The elements of Group 18 or VIII are best described as
(A) monoatomic gases. (B) diatomic gases. (C) metals. (D) halogens. (E) metalloids.
15. Which substance is the strongest base in aqueous solution?
(A) NH3
(B) HNO3
(C) CO2
(D) HCN
(E) NaOH
16. Which element is a metal?
(A) H
(B) Ne
(E) Pb
(C) Cl
(D) P
17. What is the approximate percent by mass of hydrogen in C2H6 (molar mass = 30 g/mol)?
(A) 6
(B) 20
(C) 24
(D) 60
(E) 80
18. How many moles of carbon are in 36 g of carbon?
(A) 2.0
(B) 3.0
(C) 0.33
(D) 432
(E) 36
19. Given the balanced chemical equation
2 CuSO4 + 4 KI → 2 CuI + I2 + 2 K2SO4,
how many moles of I2 can you make from 0.40 mol of CuSO4 and excess KI?
(A) 0.80
(B) 0.40
(C) 1.0
(D) 2.0
(E) 0.20
20. What is the molar concentration of Cl- when 0.20 mol of ZnCl2 are dissolved in enough water to
prepare 3.0 L of solution?
(A) 0.67
(B) 1.5
(C) 3.0
(D) 0.13
(E) 0.60
Fall 2009
FINAL CHEM 2A
(Page 4 of 13)
Short Answer (no partial credit).
21. (6 points) Fill in the blanks with the correct ground state electron configuration (noble gas
configuration) for the given atom or the atom for the given ground state electron configuration of the
neutral atom.
Atom
Electron Configuration
I
[Ar] 3d10 4s1
22. (10 points) Circle the correct answer.
Question:
Circle the correct answer.
Which element has the smaller atomic radius?
Cl
S
Which element has the lower first ionization energy?
Li
F
Which orbital is better at shielding (screening)?
s
f
Na+
Ne
Which element can form an acidic oxide?
K
C
Which element is a better reducing agent?
W
I
Which element will more readily lose an electron?
Li
F
Core
Valence
Which species has the larger radius?
S2-
S
Which species has the smaller radius?
F+
F
Which species will most readily lose an electron?
In the atom, what electrons are most shielded
(screened) from the nucleus?
Fall 2009
FINAL CHEM 2A
(Page 5 of 13)
23. (54 points) Fill in the following table (ClF3 is done for you as an example). For the determination of
formal charge(s) consider the Lewis formula/structure with the smallest formal charges (lowest energy).
In determining the total sigma and pi bonds, use the Lewis formula/structure with the smallest formal
charges.
Molecule
Electronic
Geometry
Molecular
Geometry
ClF3
TrigonalBipyramidal
T-shape
HCN
NO2–
PCl5
XeF4
SCN-
H2SO4
Ideal
Bond
Angles
Formal Oxidation
HybridCharge(s)
State
Total σ Total π
Polar or
ization
of the Bonds in Bonds in
of the
Nonpolar
(central
underlined underlined Molecule Molecule
Molecule
atom)
element element
90º,180º polar
sp3d
0
-1
3
0
Fall 2009
FINAL CHEM 2A
(Page 6 of 13)
Partial Credit. Show ALL Your Work.
24. (12 points)
A molecule that contains only carbon and oxygen is found to be 52.94% carbon by mass.
a) What is the empirical formula for the compound?
Empirical Formula:
b) Draw the Lewis structure/formula of the molecule (in this case the empirical formula is also the
molecular formula).
25. (9 points)
Vision is initiated by a photoisomerism of the molecule retinal. The molecular structure of all trans
retinal is shown below. Considering this molecule:
(A) (2 points) What is the total number of π-bonds?
____________
(B) (2 points) What is the hybridization of the C-atom marked “A”?
____________
(C) (2 points) What is the hybridization of the C-atom marked “B”?
____________
Fall 2009
FINAL CHEM 2A
(Page 7 of 13)
26. (5 points)
You are mixing X ml of wine, which is 0.0030 M in sugar, with 20.0 ml of wine, which is 0.00010 M in
sugar. The resulting wine is mixed with 30.0 ml of wine, which is 0.0020 M in sugar. The resulting
wine is 0.0015 M in sugar. What is the value of X? Assume that the volumes are additive.
Volume of wine =
27. (6 points)
A balloon is filled with nitrogen dioxide gas to an initial volume of 1.20 L. Two thirds of the nitrogen
dioxide molecules react to form the dimer, dinitrogen tetroxide. The temperature, and the external
pressure (and hence the total pressure of the balloon) are kept constant. What is the final volume of the
balloon after the reaction is completed? Assume the balloon is indefinitely expandable.
Final Volume =
Fall 2009
FINAL CHEM 2A
(Page 8 of 13)
28. (15 points)
A valve connects two gas reaction tanks. The first tank is 1.23 L and contains oxygen gas at 724
mmHg. The second tank is 2.05 L and contains nitrogen gas at 698 Torr. When the valve is opened the
gases react to form N2O. Assuming the reaction takes place at 25.0oC:
(A) What is the limiting reagent and how many moles of N2O are produced?
Limiting Reagent:
Moles N2O Produced:
(B) How many moles of the excess reagent remain after the reaction?
Mols excess reagent:
(C) What is the pressure of N2O formed?
Pressure of N2O:
(D) What is the total pressure in the tanks following the reaction?
Total Pressure:
Fall 2009
FINAL CHEM 2A
(Page 9 of 13)
29. (14 points)
B2 is a paramagnetic molecule. Below are shown two possible molecular orbital energy-level schemes
for diatomic molecules of the second period elements.
(i) For both diagrams, A and B, label the molecular orbitals (π2p, σ2s*, etc.)
(ii) In both diagrams, A and B, fill in the electrons using arrows (↓ and ↑) both in the atomic and
molecular orbitals. Which of the two diagrams is consistent with B2 being paramagnetic (circle the
correct diagram)?
Fall 2009
FINAL CHEM 2A
(Page 10 of 13)
30. (11 points)
Write each of the four quantum numbers n, l, ml, and ms for all the electrons of neutral magnesium
(electron configuration written below). Use the table below to fill in your answers. When filling in the
table, start with the first electron (arrow) on the left and progressively move to the right until all
electrons are accounted for (electrons are numbered for clarity). Enter only one quantum number per
box. The first electron is done for you. You will receive one point per electron.
Electron Number: 1 2
34
56
78
9 10
11 12
Electron
Number
n
l
ml
ms
1
1
0
0
½
2
3
4
5
6
7
8
9
10
11
12
Fall 2009
FINAL CHEM 2A
(Page 11 of 13)
31. (11 points)
Balance the following chemical equation by the half-reaction method in acidic conditions. Show your
work.
P4 + NO3– → H2PO4– + NO
(A) What is the oxidized element?_________ What is the reduced element?_________
(B) Write balanced half reactions for the oxidation reaction:
(C) Write balanced half reactions for the reduction reaction:
(D) Write the overall balanced reaction
Fall 2009
FINAL CHEM 2A
(Page 12 of 13)
Solubility rules:
Compounds which are soluble or mostly soluble:
•
Group 1, NH4+, chlorates, acetates, nitrates
•
Halides (except Pb2+, Ag+, and Hg22+)
• Sulfates (except Sr2+, Ba2+, Pb2+, and Hg22+)
Compounds which are insoluble:
•
•
Hydroxides, sulfides (except above rule, and sulfides of group 2)
Carbonates, phosphates, chromates (except above rules)
Some useful equations and data:
PLEASE NOTE: Important values and equations required for calculations are given with the
respective problem. The following may or may not be of any use.
λ=
h
mυ
d=
PM
RT
Molarity =
Moles
Liter
n (moles) =
mass (g)
molar mass (g/mol)
PV = nRT
NA = 6.022 x 1023
h = 6.626x10-34 Js
1 J = 1 kg m2 s-2 = 1 N m
mL∙M = mmol
Ptotal = P1 + P2 + …
TK = ToC + 273
R = 0.0821 L atm mol-1 K-1
1 nm = 10-9 m
c = 3.00 x 108 m s-1
c = νλ
xA = nA / ntot = PA / Ptot
Ephoton = hν
Rate2/Rate1=(M1/M2)1/2
1 atm = 760 mmHg
∆E = RH(1/ni2 – 1/nf2)
∆x ⋅ ∆p =
d=
m
V
En = − RH
h
4π
me = 9.109387x10-28 g
Z2
n2
1 g = 6.022x1023 amu
∆ p = m ∆υ
RH = 2.179 x 10 -18 J
Potentially Useful Information
1 Å = 10-10 m
% Yield =
Actual Yield
Theoretical Yield
x100
Fall 2009
FINAL CHEM 2A
(Page 13 of 13)
(You may remove this page for ease of access)
Key
1
H
1.008
2.20
3
Li
6.941
0.98
11
Na
22.99
0.93
19
K
39.10
0.82
37
Rb
85.47
0.82
55
Cs
132.9
0.79
87
Fr
(223)
0.7
Atomic Number
Symbol
Atomic Mass
Electronegativity
4
Be
9.012
1.57
12
Mg
24.31
1.31
20
Ca
40.08
1.00
38
Sr
87.62
0.95
56
Ba
137.3
0.89
88
Ra
(226)
0.9
5
B
10.81
2.04
13
Al
26.98
1.61
21
22
23
24
25
26
27
28
29
30
31
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
44.96 47.90 50.94 52.00 54.94 55.85 58.93 58.70 63.55 65.38 69.72
1.36 1.54 1.63 1.66 1.55 1.83 1.88 1.91 1.90 1.65 1.81
39
40
41
42
43
44
45
46
47
48
49
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
88.91 91.22 92.91 95.94 (98) 101.1 102.9 106.4 107.9 112.4 114.8
1.22 1.33
1.6
2.16
1.9
2.2
2.28 2.20 1.93 1.69 1.78
71
72
73
74
75
76
77
78
79
80
81
Lu
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
175.0 178.5 180.9 183.9 186.2 190.2 192.2 195.1 197.0 200.6 204.4
1.27
1.3
1.5
2.36
1.9
2.2
2.20 2.28 2.54 2.00 2.04
103
104
105
106
107
109
Lr
Unq Unp Unh Uns
Une
(260)
-
6
C
12.01
2.55
14
Si
28.09
1.90
32
Ge
72.59
2.01
50
Sn
118.7
1.96
82
Pb
207.2
2.33
7
N
14.01
3.04
15
P
30.97
2.19
33
As
74.92
2.18
51
Sb
121.8
2.05
83
Bi
209.0
2.02
8
O
16.00
3.44
16
S
32.06
2.58
34
Se
78.96
2.55
52
Te
127.6
2.1
84
Po
(209)
2.0
9
F
19.00
3.98
17
Cl
35.45
3.16
35
Br
79.90
2.96
53
I
126.9
2.66
85
At
(210)
2.2
57
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
1.10 1.12 1.13 1.14 1.13 1.17
1.2
1.20
1.2
1.22 1.23 1.24 1.25
1.1
89
90
91
92
93
94
95
96
97
98
99
100
101
102
Ac
Th
Pa
U
Np
Pu
Am Cm
Bk
Cf
Es
Fm
Md
No
(227) 232.0 (231) 238.0 (237) (244) (243) (247) (247) (251) (252) (257) (258) (259)
1.1
1.3
1.5
1.38 1.36 1.28
1.3
1.3
1.3
1.3
1.3
1.3
1.3
1.3
2
He
4.003
10
Ne
20.18
18
Ar
39.95
36
Kr
83.80
54
Xe
131.3
86
Rn
(222)
-