Download Oregon State University, Summer 2009 Chemistry 121 Midterm

Oregon State University, Summer 2009 Chemistry 121
Midterm Exam 2, July 3rd, 10 am
DO NOT OPEN THIS EXAM UNTIL INSTRUCTED.
CALCULATORS ARE NOT TO BE SHARED.
Instructions :
You should have with you several number two pencils, an eraser, your notecard, your University ID Card,
and a calculator. If you have other notes with you, place them in a sealed backpack and place the backpack
OUT OF SIGHT.
Fill in the front page of the Scantron answer sheet with your last name, first name, middle initial, and student
identification number. Leave the class section number and the test form number blank.
This exam consists of 20 multiple-choice questions. Each multiple-choice question has 5 points associated
with it. Select the best answer by filling in the corresponding circle on the rear page of the answer sheet.
If you have any questions before the exam, please ask. If you have any questions during the exam, please
raise your hand to attract the attention of a proctor. The proctor will come to you.
Open and start this exam when instructed. Present your ID card when submitting the exam. Place your openended portion of this exam in the appropriate stack. You may keep the this exam, so please mark the answers
you selected on it.
Scoring :
20 multiple-choice questions @ 5 pts each
= 100 pts
Information provided
1 L = 1000 cm3 NA = 6.022 ×1023 particles/mol
A periodic table, a list of polyatomic ions, solubility rules and a list of strong acids and bases, and oxidation
number rules are provided on the next four sheets. Check to see that you have them.
Also check to see that your exam does have 20 questions on it.
Group
1
2
3
4
5
6
7
1A
2A
3B
4B
5B
6B
7B
KEY
Atomic number !
Symbol !
Atomic mass !
1
1
H
1.00794
2
3
4
5
6
7
3
4
Li
Be
6.941
9.01218
8
9
10
8B
11
12
13
14
15
16
17
18
1B
2B
3A
4A
5A
6A
7A
8A
2
1
He
H
4.00260
5
1.0079
6
7
8
9
10
B
C
N
O
F
Ne
10.811
12.011
14.0067
15.9994
18.9984
20.1797
11
12
13
14
15
16
17
18
Na
Mg
Al
Si
P
S
Cl
Ar
22.9898
24.3050
26.9815
28.0855
30.9738
32.066
35.4527
39.948
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
Ni
Cu
Zn
Ga
Ge
As
Se
Br
Kr
39.0983
40.078
44.9559
47.88
50.9415
51.9961
54.9381
55.847
58.9332
58.69
63.546
65.39
69.723
72.59
74.9216
78.96
79.904
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
85.4678
87.62
88.9059
91.224
92.9064
95.94
(98)
101.07
102.906
106.42
107.868
112.411
114.818
118.710
121.75
127.60
126.9045
131.30
55
56
57-71
72
73
74
75
76
77
78
79
80
81
82
82
84
85
86
Cs
Ba
Hf
Ta
W
Re
Os
Ir
Pt
Au
Hg
Tl
Pb
Bi
Po
At
Rn
132.905
137.327
* Rare
Earths
178.49
180.948
183.85
186.207
190.23
192.22
195.09
196.9665
200.59
204.37
207.2
208.9804
(209)
(210)
(222)
110
111
(269)
(272)
87
88
89-103
104
105
106
107
108
109
Fr
Ra
^
Rf
Ha
Sg
Ns
Hs
Mt
(223)
226.025
Actinides
(261)
(262)
(263)
(262)
(265)
(266)
*Lanthanide
Series
^Actinide
Series
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
La
Ce
Pr
Nd
Pm
Sm
Eu
Gd
Tb
Dy
Ho
Er
Tm
Yb
Lu
138.906
140.12
140.9077
144.24
145
150.4
151.96
157.25
158.9254
162.50
164.9304
167.26
168.9342
173.04
174.967
91
92
93
94
95
96
97
98
99
100
101
102
103
89
90
Ac
Th
Pa
U
Np
Pu
Am
Cm
Bk
Cf
Es
Fm
Md
No
Lr
227.028
232.0381
231.0359
238.029
237.0482
(244)
(243)
(247)
(247)
(251)
(254)
(257)
(258)
259
262
CH121 Summer 2009 Midterm 2
Strong Acids
HCl, HBr, HI
HNO3
HClO4
H2SO4
Strong Bases
LiOH, NaOH, KOH
Ca(OH)2
(slightly soluble)
Ba(OH)2
Sr(OH)2
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CH121 Summer 2009 Midterm 2
OXIDATION NUMBER RULES
• The oxidation number of a free element is always 0.
• The oxidation number of a monatomic ion equals the charge of the ion.
• The oxidation number of fluorine in compounds is -1.
• The oxidation number of hydrogen in compounds is +1.
Exception: the oxidation number of hydrogen is -1 in metal hydrides, like CaH2.
• The oxidation number of oxygen in compounds is -2.
Exception: the oxidation number of oxygen is -1 in peroxides, like BaO2.
• The oxidation number of Cl, Br, I in compounds is -1.
Exception: when combined with O or F, the preceding rules apply.
The oxidation numbers of all other elements in a compound adjust such that:
• The sum of the oxidation numbers of all of the atoms in a neutral compound is 0.
• The sum of the oxidation numbers in a polyatomic ion is equal to the charge of the ion.
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CH121 Summer 2009 Midterm 2
1.
Nitrogen forms an interesting series of oxides including N2O, NO, NO2, N2O4 and N2O5. Which of
the following statements is/are CORRECT?
1. The number of moles of N atoms in 2 moles of NO is the same as the number in 1 mole of N2O.
2. The number of moles of O atoms in 2 moles of N2O5 is the same as the number in 5 moles of NO2.
3. In 3 moles of N2O4, there are 6 moles of N atoms and 8 moles of O atoms.
4. The oxide with the greatest (mol N/ mol O) ratio is N2O.
2.
What are the coefficients needed to balance the following equation?
____ Fe2O3(s) + ____ CO(g) Æ ____ Fe(s) + ____ CO2(g)
a.
b.
c.
d.
e.
3.
1, 2, 2, 1
3, 2, 3, 1
2, 3, 2, 1
1, 3, 1, 2
1, 3, 2, 3
When the following equation is balanced, what is the ratio of the stoichiometric coefficients (b/c)?
a PbS(s) + b O2(g) Æ c PbO(s) + d SO2(g)
a.
b.
c.
d.
e.
4.
3/4
3/2
2/1
1/1
2/3
Which of the following statements is INCORRECT?
a. A combustion reaction is one in which a compound reacts with oxygen to make carbon monoxide
and water.
b. The Law of Conservation of Matter (Mass) states that the total mass of substances in a chemical
reaction does not change.
c. In a chemical reaction, the number of atoms of all types remains constant.
d. An equation is not normally written with non-integer coefficients.
e. An equation relates the number of moles of material that react and are produced.
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CH121 Summer 2009 Midterm 2
5.
Ammonia is produced industrially from the reaction of nitrogen and hydrogen.
N2(g) + 3H2(g) Æ 2NH3(g)
If I wish to make 5.0 mol NH3, how many moles of H2 will I need?
a.
b.
c.
d.
e.
6.
1.0 mol
3.0 mol
2.0 mol
2.5 mol
1.5 mol
If I start with 2 mol of F2, how many moles of SF6 will I make by the following reaction?
S8(g) + 24 F2(g) Æ 8 SF6(g)
a.
b.
c.
d.
e.
7.
24 mol
2/3 mol
8 mol
3/2 mol
4 mol
How many grams of chromium (III) chloride (molar mass 158.6 g/mol) can I make from 5.20 g of
chromium metal via the following reaction?
Cr(s) + Cl2(g) Æ CrCl3(s)
a.
b.
c.
d.
e.
8.
3.54 g
5.20 g
52.0 g
159 g
15.9 g
Glucose (C6H12O6, molar mass 180.2 g) burns in oxygen to produce carbon dioxide and water.
C6H12O6(s) + 6O2(g) Æ 6CO2(g) + 6H2O(g)
How many grams of CO2 are formed from 45.05 g of glucose?
a.
b.
c.
d.
e.
11.0 g
44.0 g
66.0 g
122. g
264. g
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CH121 Summer 2009 Midterm 2
9.
Which of the answers correctly best describes the following list of compounds?
Nitric acid (HNO3), ammonia (NH3), sucrose (C12H22O11), KCl, acetic acid (CH3COOH)
a. Strong electrolyte, weak acid, non-electrolyte, strong acid, weak electrolyte
b. Strong acid, weak base, non-electrolyte, strong electrolyte, weak acid
c. Non-electrolyte, strong acid, weak base, weak acid, strong electrolyte
d. Non-electrolyte, strong acid, strong base, weak acid, strong electrolyte
e. Weak base, weak acid, non-electrolyte, strong acid, strong electrolyte
10.
Which of the following will result in an insoluble precipitate when mixed with an aqueous Pb(NO3)2
solution?
a. HNO3 (aq)
b. NH4NO3 (aq)
c. N2(g)
d. K2SO4 (aq)
e. LiClO4 (aq)
11.
Which are the spectator ions in the following reaction?
NiCO3(aq) + 2 HCl(aq) Æ NiCl2(aq) + H2O(l) + CO2(g)
a. H+ and CO32b. Ni2+ and Clc. Ni2+ and CO32d. CO2 and H+
e. H+ and Cl-
12.
Which is the correct net ionic equation for the “molecular” equation for the reaction between
(NH4)2S(aq) + Ni(NO3)2(aq) Æ NiS(s) + 2NH4NO3(aq)
a.
b.
c.
d.
e.
S2-(aq) + Ni2+(aq) Æ NiS(s)
(NH4)2S(aq) + Ni2+(aq) Æ NiS(s) + 2NH4+(aq)
2NH4+(aq) + S2-(aq) + Ni2+(aq) + 2NO3-(aq) Æ NiS(s) + 2NH4+(aq) + 2NO3-(aq)
S2-(aq) + Ni2+(aq) + 2NO3-(aq) Æ NiS(s) + 2NO3-(aq)
Ni2+(aq) + 2NO3-(aq) Æ NiS(s) + 2NH4+(aq)
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CH121 Summer 2009 Midterm 2
13.
Which of the following statements is INCORRECT?
a. An acid is proton donor.
b. Acid plus base gives a salt and water.
c. The neutralization reaction between an acid and base can be written succinctly as H+(aq) + OH(aq) Æ H2O(l).
d. Ammonia is a proton acceptor.
e. Acetic acid is a weak acid because it dissociates 100% into acetate ions and protons.
14.
What is the oxidation number of the chromium atoms in the dichromate ion, Cr2O72-.
a.
b.
c.
d.
e.
15.
+3.
+6.
-6.
+7.
+2.
Elemental chlorine displaces bromine from potassium bromide solution
Cl2(g) + 2KBr (aq) Æ Br2(l) + 2 KCl (aq)
Which of the statements about this reaction below is CORRECT?
a. Cl2 is reduced and Br- is acting as an reducing agent.
b. K+ is oxidized and is acting as a reducing agent.
c. Br2 is reduced, Cl- is reduced and KBr is oxidized.
d. Cl2 is oxidized and Br- is acting as an oxidizing agent.
e. This is not a redox reaction.
16.
If I wish to make 125. mL of a 0.250 M solution of H2SO4, how many grams of sulfuric acid should
I take? The molar mass of H2SO4 is 98.1 g/mol.
a. 0.306 g
b. 3.06 g
c. 12.3 g
d. 24.5 g
e. 98.1 g
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CH121 Summer 2009 Midterm 2
17.
I take 10.0 mL of a 2.0 M NaCl solution, place it in a 500 mL volumetric flask and fill up the flask
with water. What is the final concentration of the NaCl solution?
a. 0.0400 M
b. 0.0200 M
c. 0.00400 M
d. 0.100 M
e. 2.00 M
18.
I prepare an (NH4)2SO4 solution that has a concentration of 0.50 M. What are the concentrations of
[NH4+] and [SO42-] in this solution?
a. [NH4+] = 1.0 M, [SO42-] = 1.0 M
b. [NH4+] = 0.50 M, [SO42-] = 0.50 M
c. [NH4+] = 1.0 M, [SO42-] = 0.50 M
d. [NH4+] = 0.50 M, [SO42-] = 1.0 M
e. [NH4+] = 0.25 M, [SO42-] = 0.50 M
19.
Which of the following statements about a titration is INCORRECT?
a. The equivalence point of an acid-base titration can be detected by the choice of the correct
indicator.
b. A volumetric flask contains an accurate volume of liquid.
c. An acid-base titration can work if you add either base to acid, or acid to base.
d. A titration of the same volume of 1 M HCl and 1 M H2SO4 will need the same volume of 1 M
NaOH.
e. Titrations can be used for redox reactions as well as acid-base reactions.
20.
I perform the following acid/base neutralization titration.
HCl(aq) + NaOH(aq) -------> NaCl(aq) + H2O(l)
25.0 mL of hydrochloric acid solution of unknown concentration required 50.0 mL of 1.00 M sodium
hydroxide solution to be neutralized. What is the concentration of the acid?
a. 0.50 M
b. 1.00 M
c. 2.00 M
d. 2.50 M
e. 5.00 M
8