Chem E-1a: Exam 1 Review
Exam 1 will cover:
Lectures 1-3
Textbook Chapters 1-4
Practice Problems pp. 1-20
Problem Sets 1-3
Labs 1-3 (Chem E-1a only)
Practice Exams are posted on the course website. We encourage you to take these exams
under exam-like conditions. Practice Exam 1C will be discussed in sections this week.
Note: This review does NOT necessarily cover all topics that will appear on the exam. Any
material included in the indicated exam coverage above could appear on the exam.
The following problems are all taken from a previous Chem E-1a exam…
Useful Information:
Avogadro’s Number = 6.02 × 1023
Density of water at 25°C = 1.00 g/mL
Unit Conversions:
1 mL = 1 cm3
1 foot = 12 inches
1 inch = 2.54 cm
1 pound = 453.6 grams
27
Co
28
Ni
29
Cu
30
Zn
Fr
Cs
227.03
Ac
138.91
89
La
Y
88.91
57
(261)
Rf
178.49
104
Hf
Zr
91.22
72
47.88
40
Actinide series
Lanthanide series
Ra
Ba
Sr
44.96
39
231.04
Pa
232.04
Th
140.91
91
140.12
90
59
Pr
58
Ce
(263)
183.85
[106]
W
Mo
95.94
74
52.00
42
(262)
Ha
180.95
105
Ta
Nb
92.91
73
50.94
41
238.03
U
144.24
92
60
Nd
(262)
186.21
[107]
Re
Tc
(98)
75
54.94
43
237.05
Np
(145)
93
61
Pm
(265)
190.20
[108]
Os
Ru
101.07
76
55.85
44
(244)
Pu
150.36
94
62
Sm
(266)
192.22
[109]
Ir
Rh
102.91
77
58.93
45
(243)
Am
151.96
95
63
Eu
195.08
Pt
Pd
106.42
78
58.69
46
(247)
Cm
157.25
96
64
Gd
196.97
Au
Ag
107.87
79
63.55
47
(247)
Bk
158.93
97
65
Tb
200.59
Hg
Cd
112.41
80
65.39
48
(251)
Cf
162.50
98
66
Dy
204.38
Tl
In
114.82
81
69.72
49
Ga
(252)
Es
164.93
99
67
Ho
207.20
Pb
Sn
118.71
82
72.61
50
Ge
(257)
Fm
167.26
100
68
Er
208.98
Bi
Sb
121.76
83
74.92
51
As
(258)
Md
168.93
101
69
Tm
(209)
Po
Te
127.60
84
78.96
52
Se
(259)
No
173.04
102
70
Yb
(210)
At
I
126.91
85
79.90
53
Br
35.45
35
Cl
226.03
26
Fe
S
32.07
34
19.00
17
(223)
25
Mn
P
30.97
33
16.00
16
137.33
88
24
Cr
Si
28.09
32
14.01
15
132.91
87
V
23
Al
26.98
31
12.01
14
87.62
56
Rb
Ca
Mg
10.81
13
(260)
Lr
174.97
103
71
Lu
(222)
Rn
Xe
131.29
86
83.80
54
Kr
Ar
39.95
36
20.18
18
Ne
85.47
55
Ti
22
F
40.08
38
21
Sc
O
39.10
37
K
Na
Li
24.31
20
N
9
22.99
19
C
8
9.012
12
B
7
6.941
11
Be
6
4.003
10
5
4
1.008
3
2
He
H
1
PERIODIC TABLE OF THE ELEMENTS
1
1.
Calcium chloride, CaCl2, is an ionic solid that is frequently used as both a drying agent
(desiccant) and an ice-melting chemical. The density of calcium chloride is 2.15 g/mL.
a)
The most common isotope of calcium is calcium-40. Determine the number of
protons (p), neutrons (n), and electrons (e) in one ion of 40 Ca2+ .
# of p =
b)
# of n =
# of e =
Determine the number of chloride ions contained in 1.00 pound of calcium chloride.
number of chloride ions =
c)
Determine the mass in kilograms of 1.00 cubic foot of calcium chloride.
mass =
d)
ions
kg
Determine the percent by mass of calcium in calcium chloride.
percent by mass of calcium =
%
2 (Chem E-1a)
2.
In the lab, you place some copper powder into a crucible and heat it in air.
Some of the copper reacts with oxygen in the air, forming solid copper (II) oxide. You
collect the following data during the experiment:
Mass of empty crucible: 11.452 g
Mass of crucible and copper powder before heating: 12.576 g
Mass of crucible and contents after heating: 12.652 g
a)
Write a complete, balanced equation for the reaction of copper with oxygen as described
above. (Please include state symbols such as (s), (aq), etc.)
b)
Determine the mass of copper (II) oxide formed in this reaction.
mass of CuO =
c)
Determine the percent yield of this reaction.
percent yield =
d)
As you can see from your answer to part (c), this reaction did not go to completion. In an
attempt to increase your percent yield, you return the crucible to the flame and continue
to heat it for an additional ten minutes. However, even after this extensive heating, the
final mass of the crucible and contents has not increased further. In the space below,
briefly explain why this reaction doesn’t proceed to completion.
2 (Chem E-1ax)
2.
Upon heating, solid copper will react with oxygen gas to form solid copper (II) oxide.
a)
Write a complete, balanced equation for the reaction of copper with oxygen as described
above. (Please include state symbols such as (s), (aq), etc.)
b)
Is this an oxidation-reduction reaction?
(circle)
yes
no
1.124 grams of copper powder are heated in the presence of oxygen gas. The copper and
oxygen react, but this reaction does not go to completion. When the reaction is stopped,
the total mass of both the unreacted copper and the copper (II) oxide product combined is
1.200 grams.
c)
Determine the mass of oxygen gas that reacted with the copper in this reaction.
mass of O2 =
d)
Determine the mass of copper (II) oxide formed in this reaction.
mass of CuO =
e)
Determine the percent yield of this reaction.
percent yield =
3
3.
Compound X is an unknown liquid that contains only the elements C, H, and S.
a)
When 5.00 grams of Compound X are completely combusted in excess oxygen gas, the
only products of combustion are CO2 (g), H2O (l), and SO2 (g). All of the carbon
dioxide and sulfur dioxide products are collected and isolated, and 7.10 g of CO2 and
5.16 g of SO2 are collected. Determine the empirical formula of Compound X.
empirical formula:
b)
When 5.00 grams of Compound X are titrated with 0.600-molar Ba(OH)2, it is discovered
that Compound X is a monoprotic acid, and 67.2 mL of 0.600-molar Ba(OH)2 are required
to completely neutralize the sample. Determine the molecular formula of Compound X.
molecular formula:
c)
Write a complete, balanced equation for the combustion of liquid Compound X.
(Please include state symbols such as (s), (aq), etc.)
4
4.
a)
Write the chemical formula for each of the following species.
Dinitrogen Tetroxide
Ammonia
Magnesium Permanganate
Silver Carbonate
b)
Write an acceptable chemical name for each of the following.
CuSCN
SO3
H2SO4
c)
Write the oxidation state of each atom in the box above the atom.
Fe(NO3)3
d)
Na2O2
Consider the following unbalanced neutralization and precipitation reaction:
H3PO4 (aq) + Ba(OH)2 (aq) !
Ba3(PO4)2 (s) + H2O (l)
If 3 moles of H3PO4 (aq) are mixed with 3 moles of Ba(OH)2 (aq) and this reaction
proceeds to completion, how many moles of Ba3(PO4)2 (s) will be formed?
(Hint: Be sure to balance the reaction first!)
# of moles of barium phosphate =
e)
Solid barium will react with liquid water to form aqueous barium hydroxide and hydrogen
gas. In the box below, write a complete balanced equation for this chemical reaction.
(Be sure to include state symbols such as (s), (aq), etc.)
f)
In the reaction you wrote for part (e) above, the barium is being: (circle the best choice)
a) Neutralized
b) Combusted
c) Precipitated
d) Oxidized
e) Reduced
4
(space for additional work)
5
5.
The following two solutions are mixed together:
200.0 mL of 0.300-molar lead (II) nitrate, Pb(NO3)2
300.0 mL of 0.300-molar sodium fluoride, NaF
A white precipitate is formed in an exchange reaction.
a)
Write a complete, balanced equation, and then a net ionic equation for this chemical
reaction. (Please include state symbols such as (s), (aq), etc.)
Complete:
Net Ionic:
b)
Calculate the mass of the lead (II) fluoride precipitate that would be formed, assuming
the reaction goes to completion, and determine the molar concentration of all ions in the
resulting solution. (Note: Assuming that the reaction goes to completion, some of the
concentrations may be effectively zero.)
mass of PbF2 formed =
[Pb2+] =
[Na+] =
[NO3–] =
[F–] =
5
(space for additional work)
6
6.
You are given a steel vessel containing a mixture of methane gas (CH4 (g)) and propane
gas (C3H8 (g)). You completely combust this entire mixture in the presence of excess
oxygen gas, and you collect all of the carbon dioxide and water formed in the combustion
reaction. A total of 48.4 grams of CO2 and 32.4 grams of H2O are collected.
a)
In the boxes below, write complete balanced reactions for the combustion of CH4 (g) and
C3H8 (g). (Please include state symbols such as (s), (aq), etc.)
b)
Determine the number of moles of CH4 (g) and C3H8 (g) that were present in the initial
mixture.
number of moles of CH4 (g) =
moles
number of moles of C3H8 (g) =
moles