Kinetics – Let’s Get Moving – Study Guide
1. Consider the reaction X + Y
a. Rate = k[Y]
b. Rate = k[X]2[Y]
c. Rate = k[X][Y]2
d. Rate = k[X]2
e. Rate = k
Z. Which rate law corresponds to a zero order reaction”
2. Consider the reaction X + Y
Z. Which rate law corresponds to a reaction where halving the
concentration of Y would lead to no change in the rate of the reaction?
a. Rate = k[Y]
b. Rate = k[X]2[Y]
c. Rate = k[X][Y]2
d. Rate = k[X]2[Y[
e. Rate = k[X]
3. Consider the following proposed mechanism for a reaction.
Step 1: X + Y
A + Z
Step 2: Z + X
D
Which of the following shows the overall reaction?
a. X + Y A + D
b. 2X + Y
A+D
c. 2X + Y + Z
A+D
d. 2X + Y + Z
Z+A
e. None of the above
4. Consider the previous proposed mechanism for a reaction. What species is an intermediate?
a. X
b. Y
c. Z
d. A
e. D
5. Consider the previous proposed mechanism for a reaction. Given that the rate law for the
reaction is found to be Rate = k[X][Y], which step in the mechanism is the slowest?
a. Step 1
b. Step 2
c. Not enough data to tell
d. A combination of Step 1 and Step 2
e. None of the above
6. Consider the data below, for the reaction A + B
Experiment
[A] M
[B] M
1
1
2
2
3
1
a. 1
b. 2
c. 3
d. Cannot determine from the data
e. None of the above
X. What is the order with respect to [A]?
Rate mol/L sec
1
2 x 10-3
1
2 x 10-3
2
8 x 10-3
7. Using the data from #6, determine the rate law.
a. Rate = [B]2
b. Rate = k[A][B]
c. Rate = k[A]2
d. Rate = k[B]2
e. Rate = k
8. Using the data from #6, all of the following will increase the rate of the reaction, EXCEPT:
a. Increasing the concentration of B
b. Increasing the temperature
c. Adding a catalyst
d. Increasing the concentration of A
e. All of the above
9. Which best explains how catalysts increase the rate of a chemical reaction?
a. They reduce the amount of product
b. They increase the amount of product
c. The reduce the amount of reactant
d. The raise the temperature of the reaction
e. They reduce the activation energy of the reaction.
10. What is the effect of a catalyst on the reaction N2 + 3H2
a. It increase the percent of ammonia at equilibrium
b. It decrease the percent of ammonia at equilibrium
c. It decrease the rate of the reverse reaction
d. It changes the time needed to reach equilibrium
2NH3 ?
11. Why does flour burn slowly when in a pile, but rapidly when blown into the air?
a. Dispersing the particles allows more energy to be released
b. Dispersed particles have a greater surface area in contact with the air
c. The H of the dispersed particles is greater
d. Air circulating around the particles distributes heat more easily
12. Ammonia is produced by the reaction in #10. If the ammonia concentration increases from
0.288M to 0.736M in 12.0 minutes, what is the average rate of decomposition of hydrogen?
a. -0.112 mol/L min
b. -0.037 mol/L min
c. -0.056 mol/L min
d. -0.012 mol/L min
13. At a particular temperature, N2O5 decomposes according to a first order rate law with a half-life
of 3.0 sec. If the initial concentration of N2O5 is 1.0 x 1016 molecules/cm3, what will be the
concentration in molecules/cm3 after 10.0 seconds?
14. Ammonium cyanate, NH4NCO, rearranges in water to give urea, (NH2)2CO:
NH4NCO
(NH2)2CO
Experiment
[NH4NCO]
Time (min)
1
0.458
0
2
0.370
45.0
3
0.292
107
4
0.212
230
5
0.114
600
A. Using the data above, determine the order of the reaction.
B. Calculate k for the reaction
C. Calculate the half-life of ammonium cyanate under these conditions.
D. Calculate the concentration of NH4NCO after 12.0 hours.
15.
2HgCl2 + C2O42Experiment
2Cl- + 2CO2 + Hg2Cl2
Initial [HgCl2]
Initial [C2O42-]
1
0.0836
2
0.0836
3
0.0418
4
0.0316
A. What is the rate law for the above reaction?
Rate of Cl- formation
(mol/L min)
0.52 x 10-4
2.08 x 10-4
1.06 x 10-4
1.27 x 10-4
0.202
0.404
0.404
???
B. Calculate the rate constant with units
C. What is the initial rate of disappearance of C2O42- in Experiment #1?
D. Calculate the initial oxalate ion concentration for Experiment #4.
16.
2N2O5
4NO2 + O2
Time (s)
0
100
300
600
900
A. Calculate Ea for this reaction.
rate = -[N2O5]/t
[N2O5] at 338K
1.00 x 10-1 M
6.14 x 10-2 M
2.33 x 10-2 M
5.41 x 10-3 M
1.26 x 10-3 M
[N2O5] at 318K
1.00 x 10-1 M
9.54 x 10-2 M
8.63 x 10-2 M
7.43 x 10-2 M
6.39 x 10-2 M
17. For a second order reaction NO + O3
NO2 + O2, the rate constant has been measure to be
1.08 x 107mol/L sec at 298K and the activation energy has been measured to be 11.4 kJ/mol
over the temperature range 195K to 304K. What is the rate constant at 235K?
18. The decomposition of N2O5 to NO2 and NO3 is a first order gas-phase transition reaction. At 25C,
the reaction has a half-life of 2.81 seconds. At 45C, the reaction has a half-life of 0.313 seconds.
What is the activation energy of the reaction?
19. In the reaction PCl3 + Cl2
PCl5 , the forward reaction is first order in both PCl3 and Cl2 and
the reverse reaction is first order in PCl5.
A. Suppose that 2 moles of PCl3 and 1 mole of Cl2 are mixed in a closed container at constant
temperature. Draw a graph that shows how the concentration of PCl3, Cl2, and PCl5 change
with time until after equilibrium has been firmly established.
B. Give the initial rate law for the forward reaction.
C. Provide a molecular explanation for the dependence of the rate of the forward reaction on
the concentration of the reactants.
D. Provide a molecular explanation for the dependence of the rate of the forward reaction on
temperature.
20. The following results were obtained when the following reaction occurred at 25C.
2ClO2 + F2
2ClO2F
Experiment
1
2
3
Initial [ClO2] M
Initial [F2] M
0.010
0.10
0.010
0.40
0.020
0.20
A. Calculate the rate law expression of the reaction.
Intial Rate of increase
[ClO2F] mol/L sec
2.4 x 10-3
9.6 x 10-3
9.6 x 10-3
B. Calculate the numerical value of the rate constant and specify its units.
C. In experiment 2, what is the initial rate of decrease of [F2]?
D. Which of the following reaction mechanisms is consistent with the rate law developed in part A.
Justify your choice.
I.
ClO2 + F2
ClO2F2 fast
ClO2F2
ClO2F + F slow
ClO2 + F
ClO2F fast
II
F2
2F slow
2(ClO2 + F
ClO2F) fast