Chapter 13 – Chemical Kinetics
98.
When acetaldehyde at a pressure of 364 mmHg is introduced into an evacuated 500. mL flask at 518C, the half-life for the
second-order decomposition process, CH3CHO → CH4 + CO, is 410. s. What will the total pressure in the flask be after 1.00
hour?
99. The first-order decomposition of SO2Cl2 to sulfur dioxide gas and chlorine gas at 320C
has a half-life of 8.75 hr. If 600. mmHg of pure SO2Cl2 is placed in a 5.00-L flask at 320C,
how long does it take for the total pressure in the flask to rise to 1.000 atm?
Chapter 13 – Chemical Kinetics
100.
The first-order decomposition of phosphene to phosphorus and hydrogen, shown below,
4PH3(g) → P4(g) + 6H2(g)
has a half-life of 35.0 s at 680C. Starting with 520 mmHg of pure phosphene in an 8.00-L flask at 680C, how long will it
take for the total pressure in the flask to rise to 1.000 atm?
Chapter 13 – Chemical Kinetics
101.
Aspirin, C9H8O4, slowly decomposes at room temperature by reacting with water in the atmosphere to produce acetic acid,
HC2H3O2, and 2-hydroxybenzoic acid, C7H6O3 (this is why old bottles of aspirin often smell like vinegar):
C9H8O4 + H2O → HC2H3O2 + C7H6O3
Concentration and rate data for this reaction are given below.
Write the rate law for this reaction and calculate k (be sure to include the correct units).
102. Given the rate law for a reaction, rate = k[A][B]2, where rate is measured in units of M s–
1, what are the units for the rate constant k?
Chapter 13 – Chemical Kinetics
103. Given the rate law for a reaction, rate = k[A]2, where rate is measured in units of M min–
1, what are the units for the rate constant k?
104. A nuclear stress test utilizes a gamma-emitting radioisotope such as thallium-201 to
follow the flow of blood through the heart – first at rest, and then under stress. The first-order
rate constant for the decay of thallium-201 is 9.5 x 10–3 hr–1. Calculate how long it takes for
the amount of thallium-201 to fall to 5.0% of its original value.
Chapter 13 – Chemical Kinetics
105. An experimental drug, D, is known to decompose in the blood stream. Tripling the
concentration of the drug increases the decomposition rate by a factor of nine. Write the rate
law for decomposition of D.
106.
Use the table of data shown below to calculate the average rate of the reaction A→B between 10 s and 20 s.
Chapter 13 – Chemical Kinetics
107.
What is the rate law that corresponds to the data shown for the reaction 2A + B → C?
108. The rate constant for a certain first-order reaction is 0.40/min. What is the initial rate in
mole/L·min, if the initial concentration of the compound involved is 0.50 mol/L?
Chapter 13 – Chemical Kinetics
109.
At a certain temperature, the data below were collected for the reaction below.
2ICl + H2 → I2 + 2HCl.
Determine the rate law for the reaction.
Chapter 13 – Chemical Kinetics
110.
At a certain temperature, the data below were collected for the reaction below.
2ICl + H2 → I2 + 2HCl.
Determine the rate constant for the reaction.
Chapter 13 – Chemical Kinetics
111.
Nitrogen pentoxide decomposes by a first-order process yielding N2O4 and oxygen.
2N2O5 → 2N2O4 + O2
At a given temperature, the half-life of N2O5 is 0.90 hr. What is the first-order rate constant for N2O5 decomposition?
112.
For the first-order reaction 2N2O5 → 2N2O4 + O2 at a particular temperature, the half-life of N2O5 is 0.90 hr. What fraction of
the initial concentration of N2O5 will remain after 2.4 hours?
Chapter 13 – Chemical Kinetics
113. The rate constant for the first-order decomposition of C4H8 at 500C is 9.2 10–3 s–1.
How long will it take for 10.0% of a 0.100 M sample of C4H8 to decompose at 500C?
114.
The reaction 2A + B → products is second order with respect to A and zero-order with respect to B. Starting with 0.135 M of
A, what is the concentration of A after 35 min if the rate constant is 0.11 M-1s-1?
Chapter 13 – Chemical Kinetics
115.
The reaction 2A → products is second order with respect to A. If the concentration of A drops from 1.05 M to 0.815 M in a
time of 15.0 min, what is the rate constant for this reaction (the same time units may be used)?
116. The activation energy for a certain reaction is 113 kJ/mol. By what factor (how many
times) will the rate constant increase when the temperature is raised from 310 K to 325 K?
Chapter 13 – Chemical Kinetics
117.
Select True or False: Nitric acid is formed by the gas-phase hydrolysis of N2O5. The energy profile curve for the reaction
N2O5 + H2O → 2HNO3 is shown here. The reaction is endothermic and the activation energy of the reverse reaction is larger
than for the forward reaction.
Chapter 13 – Chemical Kinetics
118.
Nitric acid is formed by the gas-phase hydrolysis of N2O5. For the reaction N2O5 + H2O → 2HNO3, Ea(forward) = 15 kJ/mol
and Ea(reverse) = 51 kJ/mol. Calculate Hrxn.
Chapter 13 – Chemical Kinetics
119.
Select True or False: The oxidation of iodide ions by arsenic acid in acidic aqueous solution occurs according to the net
reaction H3AsO4 + 3I– + 2 H3O+ → H3AsO3 + I3– + H2O. The experimental rate law for this reaction is
Rate = k [H3AsO4] [I–] [H3O+].
According to the rate law for the reaction, an increase in the concentration of hydronium ion increases the rate of reaction
(linearly with increasing H+ concentration).
120.
For the following exothermic reaction, the rate law at 298 K is rate = k [H2][I2].
H2(g) + I2(g) → 2HI(g)
Which of the following, if any, would cause the rate of the reaction to increase?
a. Addition of hydrogen gas at constant temperature and volume
b. Increase in volume of the reaction vessel at constant temperature
c. Addition of a catalyst
d. Increase in temperature
Chapter 13 – Chemical Kinetics
121. Hydrogen peroxide decomposes to water and oxygen gas, and the activation energy for
this process is 42 kJ/mol. The hydrogen peroxide formed in biological processes is harmful to
tissue, but the enzyme catalase catalyzes the decomposition of hydrogen peroxide by
lowering the activation energy to 7.0 kJ/mol. Assuming the frequency factor is the same for
both processes and independent of temperature, calculate the temperature required for the
uncatalyzed decomposition to proceed at the same rate as the enzyme-catalyzed
decomposition at 37C (normal human body temperature).
122.
Select True or False: It is possible for the following overall reaction to consist of a one step mechanism:
2A + B + C → products
Chapter 13 – Chemical Kinetics
123.
Select True or False: It is possible for the following overall reaction to consist of a one step mechanism:
2A → products
124.
Select True or False: In the reaction, 2N2O → 2N2 + O2, oxygen and nitrogen gases are formed at the same rate (mol/L·s).
125.
Select True or False: The rate constant of a first-order reaction, A → products, can be determined from a graph of ln[A]
versus t.
Chapter 13 – Chemical Kinetics
126.
Select True or False: For the first-order reaction, A → products, if half of the initial concentration of A reacts in 20 min, then
the remaining half will completely react in the next 20 min.
127.
Select True or False: Substitute natural gas can be synthesized by passing carbon monoxide and hydrogen over Ni or Co at
400C.
This process is an example of homogeneous catalysis.
Chapter 13 – Chemical Kinetics
128.
Select True or False: The rate law predicted by the following two-step mechanism is rate = k[A][B].
129.
Select True or False: The rate determining step in the following mechanism is bimolecular.
Chapter 13 – Chemical Kinetics
130.
Select True or False: B is a catalyst in the following mechanism:
131. Select True or False: The rate determining step must be the first step of a reaction