Practice Exam 4 – Kinetics and Nuclear Chemistry
See Useful Information and Equations at end of test
Multiple Choice (2 points for each correct answer)
_____1. As the temperature of a reaction goes up,
A) the molecules collide with increasingly better orientation
B) the activation energy will decrease
C) the reaction order will increase
D) more molecules will have kinetic energy greater than Ea
E) all of the above are true
F) none of the above are true
_____2. Given a reaction: 2 N2O5 (g) ––––> 4 NO2 (g) + O2 (g). The reaction rate in
terms of NO2 (g) is measured to be 8 x 10–3 M/min. What is the reaction rate expressed in
terms of N2O5 (g).
A) – 64 x 10–3 M/min
D) – 4 x 10–3 M/min
–3
B) – 8 x 10 M/min
E) – 2 x 10–3 M/min
C) – 16 x 10–3 M/min
F) insufficient information
_____3. Which of the following is an example of a nuclear decay process?
30
 14
Si  0
A) 30
15 P
B) 49 Be + 12H  105 B + 01n
+ 01n  235
+ 00
C) 234
92 U
92 U



D)
7
3
Li
+
1
0
n

4
2
He
+
3
1
H
+
1
0
n
_____4. A reaction has a rate law with a rate constant of 1.7 x 10–4 M–2s–1. What is the
overall reaction order for this reaction?
A) 0th
B) 1st
C) 2nd
D) 3rd
E) 4th
F) not enough information
59
Cu is unstable with a half life of 82 s. The molar mass of
_____5. The isotope 29
naturally occurring Cu is 63.54 g/mol. What is a likely decay mechanism for this
unstable isotope of Cu. State all that apply.
A) –10 decay
B) 0 decay
C) 00  emission
D) electron capture


____6. Which of the following could have the greatest effect on the activation energy, Ea,
of a reaction?


A) increasing the temperature
B) adding a catalyst
C) increasing the reactant concentration
D) having a spontaneous reaction (∆G = –)
E) all of these
_____7. The reaction A  B is first-order overall and first-order with respect to the
reactant A. The result of doubling the initial concentration of A will be to
A) shorten the half-life of the reaction
B) lengthen the half-life of the reaction
B) increase the rate constant of the reaction
C) decrease the rate constant of the reaction
E) double the initial rate
Please refer to the following mechanism for problems 8-10.
OCl– + H2O <–––––> HOCl + OH–
I–
+ HOCl <–––––> HOI + Cl–
HOI + OH– <–––––> H2O + OI–
_____8. Which of the species shown in the mechanism above is an intermediate? List all
that apply.
A) OCl–
B) H2O
C) HOCl
D) OH–
E) I–
–
–
F) HOI
G) Cl
H) OI
I) none of these
_____9. Which of the species shown in the mechanism above is a catalyst? List all that
apply.
A) OCl–
B) H2O
C) HOCl
D) OH–
E) I–
F) HOI
G) Cl–
H) OI–
I) none of these
_____10. What is the molecularity of the second step in the mechanism?
A) unimolecular
B) bimolecular
C) termolecular
D) can not determine
11. (6 pts) For a system that is 0th order, fill in the times that would correspond with the indicated
concentrations. Keep it simple and clean! No extensive calculations needed
Time passed:
0
100 min
__________
__________
__________
[A]:
1.0 M
0.50 M
0.25 M
0.125 M
0.0625 M
12. (7 pts) Balance the following nuclear processes.
246
96
Cm
i.
ii.

iii.


7
3
Li
32
17
+
Cl
_____________ 
+

1
0
n

16
4
2
He
_________
254
102
No
 5 01n
+ __________ +
+ ________
1
0
n
13. (8 pts) Draw a reaction coordinate diagram for a reaction with the following attributes
(characteristics): ∆H°rxn is endothermic, has a two step mechanism, and whose first step is much
faster than the second step. Clearly identify the Ea for each step of the reaction in the forward
direction. Indicate the transition state(s) and the location(s) of the intermediates. Label the axes.
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14. (4 pts) Sucrose, C12H22O11, decomposes to fructose and glucose in acid solution.
When ln [sucrose] is plotted vs. time, a straight line with slope of -0.208 hr-1 results.
What is the rate law for the reaction?
15. (8 pts). Consider the following mechanism for the oxidation of bromide ions by
hydrogen peroxide in aqueous acid solution.
H+ + H2O2
H2O+–OH (rapid equilibrium)
+
H2O –OH + Br  HOBr + H2O (slow)
HOBr + H+ + Br-  Br2 + H2O (fast)
A) What is the overall reaction equation for this process?
B) Determine the rate law for this reaction?
16. (8 pts) For the reaction
OCl- + I-  OI- + Clthe following data were collected at constant temperature.
Initial [OCl-]
Initial [I-]
Initial [OH-]
Initial Rate
(mol/L)
(mol/L)
(mol/L)
(mol/(L·min))
1
0.0040
0.0020
1.00
4.9  10-4
2
0.0020
0.0040
1.00
5.0 x 10-4
3
0.0020
0.0020
1.00
2.5 x 10-4
4
0.0020
0.0020
0.50
5.0 x 10-4
A) Determine the rate law for this reaction. Use appropriate calculations.
Trial
B) Determine the value and units for the specific rate constant.
17. (8 pts) Butadiene, C4H6 (used to make synthetic rubber and latex paints) dimerizes to
C8H12 with a rate law of rate = 0.014 L/(mol·s) [C4H6]2. What will be the concentration of
C4H6 after 3.0 hours if the initial concentration is 0.025 M?
18. (10 pts) One method of dating rocks is based on their 87Sr/87Rb ratio. The 87Rb is a
beta emitter with a half-life of 5 x 1011years. A certain rock is found to have a ratio of
87
Sr/87Rb of 0.004:1.00. What is the age of the rock?
19. (4 pts) The gas-phase conversion of 1,3-butadiene to
1,5-cyclooctadiene,
2C4H6  C8H12 was studied, providing data
shown on the plot alongside, of 1/[butadiene]
versus time. Determine the specific rate constant for
this reaction.
20. (5 pts) The radioactive isotope tritium decays with a first-order rate constant k of
0.056 year-1. What fraction of the tritium initially in a sample is still present 30. years
later?
21. (6 pts) Calculate the binding energy in Joules for 13 H which has an atomic mass of
3.01605 amu.
Useful Equations and Information
speed of light = 2.9979 x 108 m/s
Mass of proton = 1.00728 amu
Mass of neutron = 1.00866 amu
Mass of electron = 5.48580 x 10-4 amu
1 amu = 1.66 x 10-27kg
E = mc2
Rate =
- [A] at time t2 – [A] at time t1
t2 – t1
[A] at time t2 – [A] at time t1
t2 – t1
Zero Order Reaction:
[At] = [Ao] - kt
First Order Reaction:
[ ]
ln  A0   kt
[ ]
 At 
Second Order Reaction:
_1_ = kt + _1__
[At]
[A0]
Arrhenius Equation


 1
1 
ln  k 2    E a 



R  T 2 T 1 
 k1 
= -[A]
t