Chemical Kinetics

Copyright © Houghton Mifflin Company. All rights reserved. 15a–2 Close-up of a crashing wave. Source: Getty Images

Copyright © Houghton Mifflin Company. All rights reserved. 15a–3

Copyright © Houghton Mifflin Company. All rights reserved. 15a–4

Copyright © Houghton Mifflin Company. All rights reserved. 15a–5 Figure 15.1: Starting with pure nitrogen dioxide at 300°C

Copyright © Houghton Mifflin Company. All rights reserved. 15a–6 Rate Law instantaneous rate of reaction. Rate = k(phenolphthalein) the concentration of phenolphthalein in a solution that was initially M in phenolphthalein and 0.61 M in OH - ion.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–7 Examples of Rate Law 2 HI(g)  H 2 (g) + I 2 (g) CH 3 Br(aq) + OH - (aq) CH 3 OH(aq) + Br - (aq) Rate = k(CH 3 Br)(OH - ) (CH 3 ) 3 CBr(aq) + OH - (aq) (CH 3 ) 3 COH(aq) + Br - But Rate = k((CH 3 ) 3 CBr) Rate law is not related to stochiometry!

Copyright © Houghton Mifflin Company. All rights reserved. 15a–8 Decomposition of N 2 O 5

Copyright © Houghton Mifflin Company. All rights reserved. 15a–9

Copyright © Houghton Mifflin Company. All rights reserved. 15a–10 Figure 15.2: Plot of the concentration of N 2 O 5 Rate = k(N 2 O 5 )

Copyright © Houghton Mifflin Company. All rights reserved. 15a–11 Figure 15.3: A plot of In[N ] versus time.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–12 Figure 15.4: Plot of [N 2 O 5 ] versus time for the decomposition reaction of N 2 O 5.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–13 Rate = k(X) We then test this assumption by checking concentration versus time data for the reaction to see whether they fit the first-order rate law. ln (X) - ln (X) 0 = - kt y = mx + b ln (X) = -kt + ln (X) 0

Copyright © Houghton Mifflin Company. All rights reserved. 15a–14 2 nd Order Reaction Rate = k(X) 2

Copyright © Houghton Mifflin Company. All rights reserved. 15a–15

Copyright © Houghton Mifflin Company. All rights reserved. 15a–16

Copyright © Houghton Mifflin Company. All rights reserved. 15a–17 Solution containing BrO 3 -

Copyright © Houghton Mifflin Company. All rights reserved. 15a–18 Butadiene and its dimer

Copyright © Houghton Mifflin Company. All rights reserved. 15a–19 Figure 15.5: (a) A plot of ln[C 4 H 6 ] versus t. (b) A plot of 1/[C 4 H 6 ] versus t.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–20 Figure 15.6: Plot of [A] versus t for a zero-order reaction

Copyright © Houghton Mifflin Company. All rights reserved. 15a–21 Figure 15.7: Decomposition reaction takes place on a platinum surface

Copyright © Houghton Mifflin Company. All rights reserved. 15a–22

Copyright © Houghton Mifflin Company. All rights reserved. 15a–23 Figure 15.8: Molecular representation of the elementary steps in the reaction of NO 2 and CO.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–24

Copyright © Houghton Mifflin Company. All rights reserved. 15a–25 Single Step Reaction CH 3 Br(aq) + OH - (aq) CH 3 OH(aq) + Br - (aq) Rate = k(CH 3 Br)(OH - )

Copyright © Houghton Mifflin Company. All rights reserved. 15a–26 Multiple Step Reaction (CH 3 ) 3 CBr(aq) + OH - (aq) (CH 3 ) 3 COH(aq) + Br - (aq) (CH 3 ) 3 CBr  (CH 3 ) 3 C + + Br - Slow step (CH 3 ) 3 C + + H 2 O  (CH 3 ) 3 COH 2 + Fast step (CH 3 ) 3 COH OH -  (CH 3 ) 3 COH + H 2 O Fast step

Copyright © Houghton Mifflin Company. All rights reserved. 15a–27 General Rules for Rate Law The rate of any step in a reaction is directly proportional to the concentrations of the reagents consumed in that step. The overall rate law for a reaction is determined by the sequence of steps, or the mechanism, by which the reactants are converted into the products of the reaction. The overall rate law for a reaction is dominated by the rate law for the slowest step in the reaction.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–28 The rate a which this colored solution enters the flask is determined by the size of the funnel stem, not how fast the solution is poured. Source: American Color

Copyright © Houghton Mifflin Company. All rights reserved. 15a–29 Slow and Fast reactions shown as molecular models

Copyright © Houghton Mifflin Company. All rights reserved. 15a–30 Figure 15.10: A plot showing the exponential dependence of the rate constant on the absolute temperature

Copyright © Houghton Mifflin Company. All rights reserved. 15a–31 Figure 15.11: The change in potential energy as a function of reaction progress for the reaction

Copyright © Houghton Mifflin Company. All rights reserved. 15a–32 Figure 15.12: Plot showing the number of collisions with a particular energy

Copyright © Houghton Mifflin Company. All rights reserved. 15a–33 Figure 15.13: Several possible orientations for a collision between two BrNO molecules.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–34 Figure 15.14: Plot of In(k) versus 1/T for the reaction

Copyright © Houghton Mifflin Company. All rights reserved. 15a–35 Figure 15.15: Energy plots for catalyzed and uncatalyzed pathways for a given reaction

Copyright © Houghton Mifflin Company. All rights reserved. 15a–36 Homogeneous Catalysis H 2 O 2 (aq) + I - (aq) H 2 O(aq) + OI - (aq) In the second step, the OI - ion is reduced to I - by H 2 O 2. OI - (aq) + H 2 O 2 (aq) H 2 O(aq) + O 2 (g) + I - (aq ) the first step in this reaction is the rate-limiting step,

Copyright © Houghton Mifflin Company. All rights reserved. 15a–37 Figure 15.16: Effect of a catalyst on the number of reaction-producing collisions.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–38 Figure 15.17: Heterogeneous catalysis of the hydrogenation of ethylene.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–39 Figure 15.18: The exhaust gases from an automobile engine are passed through a catalytic converter to minimize environmental damage.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–40 General structure of protein

Copyright © Houghton Mifflin Company. All rights reserved. 15a–41 Figure 15.19: Removal of the end amino acid from a protein by reaction with a molecule of water.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–42 Figure 15.20: Structure of the enzyme carboxypeptidase-A, which contains 307 amino acids.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–43 Figure 15.21: Protein-substrate interaction

Copyright © Houghton Mifflin Company. All rights reserved. 15a–44 Cutaway model of a catalytic converter used in automotive exhaust systems. Source: Delphi Automotive Systems

Copyright © Houghton Mifflin Company. All rights reserved. 15a–45 Collect samples of extremophiles from

Copyright © Houghton Mifflin Company. All rights reserved. 15a–46 A micrograph of the extremophile Archaeoglobus fulgidis, and organis that lives in the hot sediments near submarine hydrothermal vents. Source: Photo Researchers, Inc.

Copyright © Houghton Mifflin Company. All rights reserved. 15a–47 Reaction coordinate

Copyright © Houghton Mifflin Company. All rights reserved. 15a–48 Reaction coordinate

Copyright © Houghton Mifflin Company. All rights reserved. 15a–49 Rate

Copyright © Houghton Mifflin Company. All rights reserved. 15a–50 Concentration of reactant

Copyright © Houghton Mifflin Company. All rights reserved. 15a–51 Time (s); Time (s); Time (s)

Copyright © Houghton Mifflin Company. All rights reserved. 15a–52 Laser spectroscopy Source: California Institute of Technology

Copyright © Houghton Mifflin Company. All rights reserved. 15a–53 Figure 15.9: The STM images of the reaction of CO and O 2 Source: University of California, Irvine