Chemistry 112
Name
_______________________
Practice Exam 1B
Room/Section _______________________
Summer 2018!
Access ID (Email) ____________________
IMPORTANT: On the scantron (answer sheet), you MUST clearly fill your name, your student number,
section number, and test form (white cover = test form A; purple cover = test form B). Use a #2 pencil.
There are 25 questions on this exam. Check that you have done all of the problems and filled in the first 25
bubbles on the scantron. The maximum score on this exam is 25 points. Your score will be reported in
percent (max 100%).
Exam policy
● Calculators with text-programmable memory are not allowed.
● Relevant data and formulas, including the periodic table, are attached at the end of this exam.
● Your grade will be based only on what is on the scantron form.
● The answer key will be posted on ANGEL after the exam.
● You have 75 minutes to complete this exam.
● You must completely fill in your scantron bubbles before the 75 minute period has ended.
● You must turn in your cover sheet with your scantron answer form.
Hints
●
●
●
●
As you read the question, underline or circle key words to highlight them for yourself. Avoid errors
from "mis-reading" the question.
Pay attention to units and magnitudes (decimal places) of numbers obtained from calculations.
There is no penalty for guessing.
Circle the answer you choose so that you can grade yourself using the answer key posted after the
exam.
Summer Practice Exam 1A!
------------------------------------------------------------------------------------------------------------------------------1. When the concentrations of the reactants are increased, the rate of the reaction increases.
Which statement explains this behavior?
A. Increased concentration increases the fraction of molecules that have enough energy to react.
B. Increased concentration increases the frequency of the molecular collisions.
C. Increased concentration increases the rate constant.
D. Increased concentration increases the kinetic energy of the molecules.
E. Increased concentration increases the average potential energy of the molecules.
------------------------------------------------------------------------------------------------------------------------------2. In the figure below, which letter corresponds to a reaction intermediate?
------------------------------------------------------------------------------------------------------------------------------3. What would happen if the kinetic energy of the reactants were not enough to provide the needed
activation energy for a certain reaction?
A. The products would be produced at a lower energy.
B. The rate of the reaction would tend to increase.
C. The activated complex would be converted into products.
D. The reactants would not successfully form products.
E. The products would form at an unstable energy state.
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-----------------------------------------------------------------------------------------------------------------------------4. Which of the following statements regarding nuclear decay is /are True?
I.
Nuclear decay rate constants are influenced by the external pressure applied to a system.
II. Nuclear decay always adheres to first order kinetics.
III. The half-life of a nuclear decay reaction is dependent on the initial concentration of
radioactive material in a sample.
IV. Altering the temperature of a radioactive sample will influence the decay rate constant, k.
A. II only
B. III only
C. II and IV only
D. I and II only
E. I, II, and IV only
------------------------------------------------------------------------------------------------------------------------------5. A scientist runs a reaction under catalyzed and uncatalyzed conditions and generates the
following graph of her data. Which of the following statements is FALSE?
A. The activation energy for reaction a is larger in the reverse direction than in the forward
direction.
B. Curve b has one intermediate and two activated complexes.
C. Reactions a and b have the same overall energy change.
D. The activation energy for reaction b is smaller than that for reaction a.
E. Curve a is for the uncatalyzed reaction, and curve b is for the catalyzed reaction.
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------------------------------------------------------------------------------------------------------------------------------6. An isotope of 237Np undergoes 12 rounds of alpha decay and 5 rounds of beta decay. What is
the resultant daughter isotope?
A.
179
Tm
B.
184
W
C.
194
Tm
D.
189
Gd
E.
189
W
------------------------------------------------------------------------------------------------------------------------------7. At elevated temperatures, dinitrogen pentoxide decomposes to nitrogen dioxide and oxygen
according to the following reaction:
2 N2O5(g) → 4 NO2(g) + O2(g)
What is the rate of decomposition of N2O5 when the rate of formation of NO2 is 5.5 × 10–4 M/s?
A.
B.
C.
D.
E.
2.2 × 10–3 M/s
1.4 × 10–4 M/s
10.1 × 10–4 M/s
2.8 × 10–4 M/s
5.5 × 10–4 M/s
------------------------------------------------------------------------------------------------------------------------------8. SN2 reactions represent an important class of substitution reactions in organic chemistry and get
their name from the fact that they are first order with respect to both reactants (second order
overall). Consider the following SN2 reaction:
If the rate constant k = 0.0012 M–1s–1 under a given set of conditions, what is the rate if [ethoxide] =
0.0050 M and [1-bromopropane] = 0.0025?
A. 1.3 x 10–5 M/s
B. 6.0 x 10–6 M/s
C. 3.0 x 10–6 M/s
D. 1.5 x 10–8 M/s
E. 1.2 x 10–3 M/s
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------------------------------------------------------------------------------------------------------------------------------9. The following reaction profile corresponds to the isomerization of methyl isonitrile (CH3NC) to
acetonitrile (CH3CN), going from left to right. What is the overall energy change ΔE of the reverse
reaction, where acetonitrile is converted into methyl isonitrile?
A. +160 kJ/mol
B. +99 kJ/mol
C. +259 kJ/mol
D. −99 kJ/mol
E. −61 kJ/mol
------------------------------------------------------------------------------------------------------------------------------10. Phosphorous-32 is one of the most widely used radionuclides in biomedical research and
treatment. Predict the mode of radioactive decay of 32P and the resulting nuclide that is produced in
the decay process.
Answer Choice
A.
B.
C.
D.
E.
Type of Decay
Alpha decay
Beta decay
Positron emission
Alpha decay
Beta decay
Isotope
28
13
32
16
32
14
36
17
32
14
Al
S
Si
Cl
Si
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------------------------------------------------------------------------------------------------------------------------------11. Warfarin, an anticoagulant drug, has a relatively long biological first order half-life of 40 hours.
A physician wishes to administer a second dose after the first 10 mg dose has been depleted to 4
mg. How long should she wait to administer second dose of the drug?
A. 48 hours
B. 53 hours
C. 42 hours
D. 29 hours
E. 62 hours
------------------------------------------------------------------------------------------------------------------------------Please use the following reaction and experimental data for the next two questions.
------------------------------------------Consider the following ridiculously important reaction:
2 A + 2 B + C → Ridiculously Important Products
A scientist collects the following data:
Experiment
[A] (M)
[B] (M)
[C] (M)
Rate
1
0.050
0.050
0.050
2.1 x 10–3 M/s
2
0.100
0.050
0.050
8.4 × 10–3 M/s
3
0.100
0.100
0.050
8.4 × 10–3 M/s
4
0.100
0.100
0.150
2.52 × 10–2 M/s
12. Given these data, what is the overall rate law for this ridiculously important reaction?
A. Rate = k[A]2[C]
B. Rate = k[A][B][C]2
C. Rate = k[A]2[B]
D. Rate = k[A][B][C]3
E. Rate = k[A]2[C]3
------------------------------------------13. What is the rate constant for this reaction?
A. 2.1 x 10–3 M/s
B. 0.84 M–1s–1
C. 16.8 M–2s–1
D. 336 M–3s–1
E. 6720 M–4s–1
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14. The decomposition of hydrogen peroxide is first order in H2O2.
2H2O2 (aq) → 2H2O (ℓ) + O2 (g)
The rate constant for this reaction at 20°C is 1.8 x 10–5 s–1. If the starting concentration of H2O2 is
0.75 M, determine the concentration of H2O2 remaining after 6 h.
A. 0.62 M
B. 1.2 M
C. 0.51 M
D. 0.40 M
E. 4.0 M
------------------------------------------------------------------------------------------------------------------------------15. A scientist runs multiple experiments and plots the following experimental data:
Slope of trend line = –0.022 s–1
y-intercept = 2.75
Slope of trend line = 0.0045 M–1s–1
y-intercept = 0.0068 M–1
Given these data, what is the value of the rate constant, k, under these conditions?
A. 0.022 s–1
B. 2.75 s–1
C. 0.0045 M–1s–1
D. 0.0068 M–1s–1
E. –0.0045 s–1
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------16. According to the graph below, which statements are TRUE?
i. Li-6 is more likely to undergo fusion than fission
ii. Cn-285 has a more stable nucleus than U-238
iii. U-235 is more likely to undergo fission than fusion
A. ii only
B. iii only
C. ii and iii only
D. i and iii only
E. All of the above are true.
------------------------------------------------------------------------------------------------------------------------------17. The mass of a boron-11 nucleus is 10.8082571 amu. Calculate the mass defect for a boron
nucleus.
A. 8.7923157 amu
B. 0.2801148 amu
C. 2.984 amu
D. 6.0883719 amu
E. 0.2773719 amu
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18. A 1 L flask is charged with 0.124 mol of A and allowed to react to form B according to the
reaction A(g) → 3 B(g). The following data are obtained for A as the reaction proceeds:
TIme (s)
0
10
20
30
40
Moles of A
0.124
0.110
0.088
0.073
0.054
How many moles of B will be present at 40 seconds?
A. 0.054 moles B
B. 0.372 moles B
C. 0.041 moles B
D. 0.210 moles B
E. 0.023 moles B
------------------------------------------------------------------------------------------------------------------------------19. The experimentally determined rate law for the reaction below is rate = k[H2][ICl].
H2 + 2 ICl → 2 HCl + I2
Which of the following mechanisms is consistent with this rate law?
A.
Step 1: ICl + ICl → I2 + Cl2 (slow)
Step 2: Cl2 + H2 → 2 HCl
B.
Step 1: H2 + ICl → HI + HCl (slow)
Step 2: ICl + HCl → HI + Cl2
C.
Step 1: H2 → 2 H (slow)
Step 2: ICl + H → HCl + I
Step 3: H + I → HI
D.
Step 1: H2 + ICl → HCl + HI (slow)
Step 2: HI + ICl → HCl + I2
E.
Step 1: H2 → 2 H (fast)
Step 2: 2 ICl + 2 H → 2 HICl (slow)
Step 3: 2 ICl + 2 HICl→ 2 HI2 + 2 Cl2
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20. You are a world famous biochemist that has discovered the enzyme Nittanyase (NtASE). For
your last grant proposal, you wanted to know if you could enhance the catalytic activity of this
enzyme by altering its structure and creating a mutation. Below is your experimental data for 3
versions of the modified enzyme, labeled A, B or C. Which modified enzyme demonstrates the
greatest increase in catalytic activity?
NtASE-C
NtASE-B
Original NtASE
NtASE-A
A. NtASE-A
B. NtASE-B
C. NtASE-C
D. NtASE-B and NtASE-C both equally enhance the rate.
E. All modifications result in the same increase.
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------------------------------------------------------------------------------------------------------------------------------21. A scientist runs a kinetic analysis and generates the following data:
She then proposes the following mechanism. Which rate law is consistent with these data and the
proposed mechanism?
Cl2 (g) + O2 (g) → Cl2O2 (g)
Cl2O2 (g) + N2 (g) → 2 ClNO (g)
A. Rate = kobs[Cl2O2]2
B. Rate = kobs[Cl2][O2]
C. Rate = kobs[Cl2][O2][N2]
D. Rate = kobs[Cl2O2][N2]
E. Rate = kobs[Cl]2[O2]
------------------------------------------------------------------------------------------------------------------------------22. Scientists at Penn State discover a new element and dub it Nittnium! Confident that they’ll be
studying it throughout the semester as it applies to Chem 112 principles, they decide to first
determine its half-life. If it takes 4.09 minutes for 20% of a sample to decay, what is the half-life of
Nittnium?
A. 6.82 min
B. 12.70 min.
C. 1.76 min.
D. 0.43 min.
E. 3.00 min.
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------------------------------------------------------------------------------------------------------------------------------23. Madison was asked to collect data for an Arrhenius plot of a certain reaction, and her results
are shown below. The slope of the line is −1.61 x 104, and the y-intercept is 23.2. Given this plot,
at approximately what temperature will the reaction have a rate constant of k = 0.111 M–1s–1?
A.
B.
C.
D.
E.
0.00158 K
763 K
633 K
0.00143 K
298 K
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------------------------------------------------------------------------------------------------------------------------------24. Carbon-14 dating is an essential technique for determining the age of organic artifacts. Given
that the half-life of 14C decay is 5,730 years, how old is an important Alpine wooden artifact
discovered in southern Switzerland with 19% the 14C activity of modern-day wood?
A.
B.
C.
D.
E.
1.4 x 104 years
3.0 x 104 years
6.4 x 105 years
1.8 x 105 years
6.1 x 104 years
------------------------------------------------------------------------------------------------------------------------------25. Streptococcus type D is a type of bacteria responsible for spoilage in some sausages. The
metabolic processes that lead to spoilage have a calculated activation energy of 43.1 kJ/mol.
Given this information, how many times faster will sausage spoil sitting out on a hot summer day
(33°C) than in a freezer (–18°C)?
A. 3.6
B. 41.8
C. 82.1
D. 51.0
E. 29.6
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THE END! YOU DID IT! NICE!
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Answer Key
1.
2.
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8.
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25.
B
C
D
A
A
E
D
D
B
B
B
A
C
C
A
D
B
D
D
C
C
B
C
A
E