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Key Concepts PowerPoint

## Chapter 12Chemical 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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