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Key Concepts PowerPoint

Chapter 12
Chemical Kinetics

 
12-01
Title
Decomposition of N2O5
Caption
Figure 12.1 Concentrations measured as a function of time when gaseous N2O5 at an initial concentration of 0.0200 M decomposes to gaseous NO2 and O2 at 55°C. Note that the concentrations of O2 and NO2 go up as the concentration of N2O5 goes down. The slope of the hypotenuse of each triangle gives the average rate of change of the product or reactant concentration during the indicated time interval. The rate of formation of O2 is one-fourth the rate of formation of NO2 and one-half the rate of decomposition of N2O5.
Notes
Rate of decomposition of N2O5
Keywords
kinetics, rate, decomposition
12-02
Title
Instantaneous rate
Caption
Figure 12.2 Concentration of NO2 versus time when N2O5 decomposes at 55°C. The average rate of formation of NO2 during a time interval Dt equals the slope of the hypotenuse of the triangle defined by D[NO2] and Dt. As the time interval about the time t = 350 s gets smaller, the triangle shrinks to a point, and the slope of the hypotenuse approaches the slope of the tangent to the curve at time t. The slope of the tangent at time t is defined as the instantaneous rate of the reaction at that particular time. The initial rate is the slope of the tangent to the curve at t = 0.
Notes
Instantaneous rate and initial rate, slopes of the tangent to the curve
Keywords
instantaneous rate, initial rate
12-03
Title
Reaction order
Caption
Figure 12.3 Change in reaction rate when the concentration of a reactant A is doubled for different values of the exponent m in the rate law, rate = k[A]m[B]n. Note that the rate change increases as m increases.
Notes
Exponents m and n in the rate law must be determined experimentally.
Keywords
rate law, reaction order
12-05
Title
Problem 12.4
Caption
Figure 12.5 A sequence of photographs showing the progress of the reaction of hydrogen peroxide (H2O2) and iodide ion (I-). As time passes (left to right), the red color due to triiodide ion (I3-) increases in intensity.
Notes
The oxidation of iodide ion by hydrogen peroxide in an acidic solution is illustrated in Figure 12.5 in conjunction with Problem 12.4
Keywords
rate law, reaction order
12-05-01UN
Title
Key Concept Problem 12.6
Caption
The relative rates of the reaction A +B --> products in vessels (a)-(d) are 1:1:4:4. Red spheres represent A molecules and blue spheres represent B molecules.
Notes
Key Concept Problem 12.6
Keywords
rate law, reaction order
12-05-02UN
Title
First-order integrated rate law
Caption
Integrated rate law for a first-order reaction shown as an equation of a line. The rate constant k is equal to -(slope).
Notes
Integrated rate law for a first-order reaction
Keywords
12-06
Title
First-order reaction
Caption
Figure 12.6 Plots of (a) reactant concentration versus time and (b) natural logarithm of reactant concentration versus time for a first-order reaction. A first-order reaction exhibits an exponential decay of the reactant concentration (a) and a linear decay of the logarithm of the reactant concentration (b). The slope of the plot of ln [A] versus time gives the rate constant.
Notes
If a linear relationship is observed by graphing ln[A] versus time, then the reaction is first order.
Keywords
first order, integrated rate law
12-06-01UN
Title
Worked Example 12.6
Caption
Data table and graph for the decomposition of N2O5 demonstrating the reaction to be first order.
Notes
Data table and graph for Example 12.6
Keywords
rate law, integrated rate law, first order
12-07
Title
First-order half-life
Caption
Figure 12.7 Concentration of a reactant A as a function of time for a first-order reaction. The concentration falls from its initial value, [A]0, to [A]0/2 after one half-life, to [A]0/4 after a second half-life, to [A]0/8 after a third half-life, and so on. For a first-order reaction, each half-life represents an equal amount of time.
Notes
Reaction half-life for a first-order reaction
Keywords
first order, half-life
12-07-01UN
Title
Key Concept Problem 12.10
Caption
Consider the first-order reaction A --> B in which A molecules (red spheres) are converted to B molecules (blue spheres).
Notes
Key Concept Problem 12.10
Keywords
first-order, half-life
12-07-02UN
Title
Second-order integrated rate law
Caption
Integrated rate law for a second-order reaction shown as an equation of a line. The rate constant k is equal to the slope.
Notes
Integrated rate law for a second-order reaction
Keywords
second-order, integrated rate law
12-08
Title
Second-order half-life
Caption
Figure 12.8 Concentration of a reactant A as a function of time for a second-order reaction. Note that each half-life is twice as long as the preceding one because t1/2 = 1/k[A]0 and the concentration of A at the beginning of each successive half-life is smaller by a factor of 2.
Notes
Reaction half-life for a second-order reaction
Keywords
second-order, half-life
12-08-01UN
Title
Worked Example 12.8
Caption
Concentration-time data are given for the decomposition of nitrogen dioxide to nitric oxide and molecular oxygen. Plot the data using the relationships from the integrated rate laws to determine if the reaction is first-or second-order.
Notes
Worked Example 12.8
Keywords
reaction order
12-09
Title
Zeroth-order reaction
Caption
Graph of [A] versus time for a zeroth-order reaction yields a linear plot.
Notes
Zeroth-order reaction
Keywords
zeroth-order
12-10
Title
Elementary reaction steps
Caption
Figure 12.10 Elementary steps in the reaction of NO2 with CO.
Notes
Ball-and-stick representations for the elementary steps in the reaction of NO2 with CO.
Keywords
elementary steps, mechanism
12-10-01UN
Title
Unimolecular reaction
Caption
An elementary reaction that involves a single reactant molecule.
Notes
Unimolecular reaction is a first-order elementary step
Keywords
molecularity, unimolecular
12-10-03UN
Title
Bimolecular reaction
Caption
An elementary reaction that results from an energetic collision between two reactant molecules, even if the two molecules happen to be identical.
Notes
Bimolecular reaction is a second-order elementary step
Keywords
molecularity, bimolecular
12-10-04UN
Title
Termolecular reaction
Caption
An elementary reaction involving an energetic three-body collision. Reactions of this sort are rare.
Notes
Termolecular reaction is a third-order elementary step
Keywords
molecularity, termolecular
12-10-05UN
Title
Worked Example 12.9
Caption
The following two-step mechanism has been proposed for the gas-phase decomposition of nitrous oxide (N2O).
Notes
Worked Example 12.9
Keywords
molecularity, intermediates
12-10-06UN
Title
Key Concept Problem 12.12
Caption
A suggested mechanism for the reaction of nitrogen dioxide and molecular fluorine is shown.
Notes
Key Concept Problem 12.12
Keywords
molecularity, intermediates
12-11a-d
Title
Effect of Concentration on Rate
Caption
Figure 12.11 The effect of concentration on the frequency of collisions between A molecules (blue) and B molecules (red). (a) The frequency of AB collisions involving any one A molecule is proportional to the concentration of B molecules. (b) Doubling the concentration of A molecules (from 1 to 2 per unit volume) doubles the total frequency of AB collisions. (c) Doubling the concentration of B molecules doubles the frequency of AB collisions involving any one A molecule. (d) Doubling the concentration of A molecules and doubling the concentration of B molecules quadruples the total frequency of AB collisions. Thus, the total frequency of AB collisions is proportional to the concentration of A molecules times the concentration of B molecules.
Notes
Number of molecular collisions is proportional to the concentration
Keywords
rate, molecular collisions
12-11-01UN
Title
Rate law and reaction mechanism
Caption
The conversion of bromomethane to methanol in basic solution is an example of a reaction whose overall rate law is the same as the rate law for the elementary reaction.
Notes
Rate law and reaction mechanism
Keywords
rate law, mechanism, elementary reaction
12-12
Title
Proposing Reaction Mechanisms
Caption
Figure 12.12 Flowchart illustrating the logic used in studies of reaction mechanisms.
Notes
Proposing reasonable reaction mechanisms from the experimentally determined rate law
Keywords
rate law, reaction mechanism
12-13-01UN
Title
Collisions that yield product
Caption
According to collision theory, molecules must collide in the proper orientation in order for a reaction to occur. Such a collision goes through a transition state, which then yields the products.
Notes
Collision theory and transition states
Keywords
collision theory, transition state
12-14
Title
Reaction Energy Profile
Caption
Figure 12.14 Potential energy profile for the reaction A +BC --> AB +C, showing the energy barrier between the reactants and products. As the reaction progresses, kinetic energy of the reactants is first converted into potential energy of the transition state and is then transformed into kinetic energy of the products. At each point along the profile, the total energy is conserved. The profile is drawn for an exothermic reaction, so DE, the energy of reaction, is negative.
Notes
Energy is required for reactants to collide in the necessary orientation for reaction to occur (activation energy).
Keywords
activation energy, transition state, collision theory
12-15
Title
Fraction of collisions vs. collision energy
Caption
Figure 12.15 Plots of the fraction of collisions with a particular energy at two different temperatures. For each plot, the total area under the curve is unity, and the area to the right of Ea is the fraction f of the collisions with an energy greater than or equal to Ea. The fraction of collisions that are sufficiently energetic to result in reaction increases rapidly with increasing temperature.
Notes
Higher temperatures allow for a greater fraction of collisions with enough energy to surpass the activation energy "barrier"
Keywords
temperature, collisions, activation energy
12-15-01UN
Title
Collision orientation
Caption
Not all molecular collisions result in a reaction.
Notes
Significance of molecular orientation during collision
Keywords
orientation, collision theory
12-15-02UN
Title
Collision orientation
Caption
The fraction of collisions having the proper orientation for conversion of reactants to products is called the steric factor, p.
Notes
Significance of molecular orientation during collisions
Keywords
collision theory, steric factor
12-15-03UN
Title
The Arrhenius equation
Caption
Relationship between the rate constant and the activation energy of the reaction. The term pZ is usually represented with the symbol A and is called the frequency factor.
Notes
The Arrhenius equation relates rate constant, molecular collisions, activation energy and temperature
Keywords
Arrhenius equation, frequency factor
12-15-04UN
Title
Key Concept Problem 12.15
Caption
The potential energy profile for the one-step reaction AB +CD --> AC +BD is shown. The energies are in kJ/mol relative to an arbitrary zero of energy.
Notes
Key Concept Problem 12.15
Keywords
key concept, activation energy
12-15-05UN
Title
The Arrhenius Plot
Caption
According to the rearranged Arrhenius equation, the activation energy for a reaction can be determined by plotting ln k versus (1/T) which yields a line whose slope is equal to (-Ea/R).
Notes
Using the Arrhenius equation to determine activation energy of a reaction
Keywords
Arrhenius equation, activation energy
12-15-06UN
Title
Worked Example 12.11
Caption
Plot of ln k vs. (1/T) from the data for the gas-phase decomposition of hydrogen iodide.
Notes
Using the Arrhenius equation to determine activation energy of a reaction
Keywords
Arrhenius equation, activation energy
12-17a, b
Title
Effect of a Catalyst
Caption
Figure 12.17 Typical potential energy profiles for a reaction whose activation energy is lowered by the presence of a catalyst: (a) the catalyzed pathway; (b) the uncatalyzed pathway. The shape of the barrier for the catalyzed pathway describes the decomposition of H2O2: The first of the two maxima is higher because the first step is rate-determining.
Notes
Catalysts provide a lower energy pathway for the reaction to proceed without being consumed in the reaction.
Keywords
catalysis, catalysts, activation energy
12-17-01UN
Title
Key Concept Example 12.12
Caption
The relative rates of the reaction A +B --> AB in vessels (1)-(4) are 1:2:1:2. Red spheres represent A molecules, blue spheres represent B molecules, and connected yellow spheres represent molecules of a third substance C.
Notes
Key Concept Example 12.12
Keywords
key concept, rate law, mechanism, catalyst
12-17-02UN
Title
Key Concept Problem 12.17
Caption
The relative rates of the reaction 2 A +C2 --> 2 AC in vessels (1)-(4) are 1:1:2:3. Red spheres represent A molecules, blue spheres represent B molecules, and connected yellow spheres represent C2 molecules.
Notes
Key Concept Problem 12.17
Keywords
key concept, rate law, mechanism, catalyst
12-18
Title
Heterogeneous Catalysis
Caption
Figure 12.18 Proposed mechanism for the catalytic hydrogenation of ethylene (C2H4) on a metal surface. (a) H2 and C2H4 are adsorbed on the metal surface. (b) The H-H bond breaks as H-metal bonds form, and the H atoms move about on the surface. (c) One H atom forms a bond to a C atom of the adsorbed C2H4 to give a metal-bonded C2H5 group. (d) A second H atom bonds to the C2H5 group, and the resulting C2H6 molecule is desorbed from the surface.
Notes
Catalytic hydrogenation of ethylene to ethane
Keywords
heterogeneous catalysis, hydrogenation
12-19
Title
Automobile catalytic converter
Caption
Figure 12.19 The gases exhausted from an automobile engine pass through a catalytic converter where air pollutants such as unburned hydrocarbons (CxHy), CO, and NO are converted to CO2, H2O, N2, and O2. The photo shows a cutaway view of a catalytic converter. The beads are impregnated with the heterogeneous catalyst.
Notes
Catalytic converters in automobiles to help reduce offending pollutant emissions
Keywords
catalytic converter, pollutants
12-19-05UN
Title
Key Concept Summary
Caption
Chemical kinetics key concept summary.
Notes
Key concept summary Chapter 12
Keywords
key concept, summary
12-19-06UN
Title
Key Concept Problem 12.22
Caption
The following reaction is first order in A (red spheres) and first order in B (blue spheres)
Notes
Key Concept Problem 12.22
Keywords
key concept, relative rate
12-19-07UN
Title
Key Concept Problem 12.23
Caption
Consider the first-order decomposition of A molecules (red spheres) in three vessels of equal volume.
Notes
Key Concept Problem 12.23
Keywords
key concept, relative rate, half-life
12-19-08UN
Title
Key Concept Problem 12.24
Caption
Consider the first-order reaction A --> B in which A molecules (red spheres) are converted to B molecules (blue spheres).
Notes
Key Concept Problem 12.24
Keywords
key concept, half-life
12-19-09UN
Title
Key Concept Problem 12.25
Caption
The following pictures represent the progress of the reaction A --> B in which A molecules (red spheres) are converted to B molecules (blue spheres).
Notes
Key Concept Problem 12.25
Keywords
key concept, reaction order
12-19-10UN
Title
Key Concept Problem 12.26
Caption
The following pictures represent the progress of a reaction in which two A molecules combine to give a more complex molecule A2.
Notes
Key Concept Problem 12.26
Keywords
key concept, reaction order, rate law
12-19-11UN
Title
Key Concept Problem 12.27
Caption
What is the molecularity of each of the following elementary reactions?
Notes
Key Concept Problem 12.27
Keywords
key concept, molecularity
12-19-12UN
Title
Key Concept Problem 12.28
Caption
Consider a reaction that occurs by the following mechanism and has the potential energy profile shown.
Notes
Key Concept Problem 12.28
Keywords
key concept, rate-determining step, rate law, intermediate, transition state
12-19-13UN
Title
Key Concept Problem 12.29
Caption
Draw a plausible transition state for the bimolecular reaction of nitric oxide with ozone. Use dashed lines to indicate the atoms that are weakly linked together in the transition state.
Notes
Key Concept Problem 12.29
Keywords
key concept, transition state
12-TB01
Title
Table 12.1 Concentrations as a Function of Time at 55°C for the Reaction
Caption
Notes
Keywords
12-TB02
Title
Table 12.2 Balanced Chemical Equations and Experimentally Determined Rate Laws for Some Reactions
Caption
Notes
Keywords
12-TB03
Title
Table 12.3 Initial Concentration and Rate Data for the Reaction
Caption
Notes
Keywords
12-TB03.01UN
Title
Caption
Notes
Keywords
12-TB04
Title
Table 12.4 Characteristics of First-and Second-Order Reactions of the Type
Caption
Notes
Keywords
12-TB04.01UN
Title
Time (s)
Caption
Notes
Keywords
12-TB05
Title
Table 12.5 Rate Laws for Elementary Reactions
Caption
Notes
Keywords
12-TB05.01UN
Title
Temperature k Temperature k (°C) () (°C) ()
Caption
Notes
Keywords
D12-TB06
Title
Table 12.6 Some Heterogeneous Catalysts Used in Commercially Important Reactions
Caption
Notes
Keywords
12-TB06.01UN
Title
Initial Rate of Decomposition of ExperimentInitial (M/s)
Caption
Notes
Keywords
12-TB06.02UN
Title
Initial Rate of Initial ecomposition of Experiment (M/s)
Caption
Notes
Keywords
12-TB06.03UN
Title
Initial Rate of Initial Initial Consumption Experiment of (M/s)
Caption
Notes
Keywords
12-TB06.04UN
Title
Initial Rate of Initial Initial Consumption experiment[NO] of (M/s)
Caption
Notes
Keywords
12-TB06.05UN
Title
Temperature k Temperature k(°C) ()(°C) (1/s)
Caption
Notes
Keywords
12-TB06.06UN
Title
Temperature k Temperature k (°C) () (°C) ()
Caption
Notes
Keywords
12-TB06.07UN
Title
Initial Rate Initial Initial of Formation Experiment of (M/s)
Caption
Initial Rate Initial Initial of Formation Experiment of (M/s)
Notes
Keywords
12-TB06.08UN
Title
Time Experiment (s) [A] [B] [C] [D]
Caption
Time Experiment (s) [A] [B] [C] [D]
Notes
Keywords
12-TB06.09UN
Title
Experiment Time (s)
Caption
Experiment Time (s)
Notes
Keywords
12-TB06.10UN
Title
Initial Rate of Temperature Initial Decomposition Experiment (°C) of M/s)
Caption
Initial Rate of Temperature Initial Decomposition Experiment (°C) of M/s)
Notes
Keywords
12-TB06.11UN
Title
Initial Rate of Temperature Decomposition (K) Initial of (M/s)
Caption
Initial Rate of Temperature Decomposition (K) Initial of (M/s)
Notes
Keywords
12-TB06.12UN
Title
Temperature Initial Initial Initial Rate of Experiment (K)[A][B]Formation of C (M/s)
Caption
Temperature Initial Initial Initial Rate of Experiment (K)[A][B]Formation of C (M/s)
Notes
Keywords
12-TB06.13UN
Title
Time (s) Absorbance
Caption
Time (s) Absorbance
Notes
Keywords
12-TB06.14UN
Title
Temperature Initial Initial Rate ExperimentK)[HI] (M/s)
Caption
Temperature Initial Initial Rate ExperimentK)[HI] (M/s)
Notes
Keywords

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