Principles of Chemical Kinetics
|
|
- Wesley Bradford
- 5 years ago
- Views:
Transcription
1 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Reactions Summary Principles of Chemical Kinetics Ramon Xulvi-Brunet Escuela Politécnica Nacional
2 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Reactions Summary Outline 1 Kinetic Theory of Gases Statistical mechanics of gases The Maxwell-Boltzmann distribution of speeds Molecular collisions 2 Rates of Chemical Reactions Differential and integrated laws Reactions mechanisms Important types of chemical reactions 3 Theories of Chemical Reactions Collision theory Activated complex theory
3 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Chemical reactions and statistical mechanics The Maxwell-Boltzmann distribution of In other to reactions to happen molecules need to come close to be able to interact. Per unit time, the probability of interaction depends on the probability of molecules to come close. That probability is computed by means of the statistical mechanics. The simplest statistical models that allow the calculation of that probability are based on the kinetic theory of gases.
4 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Presure of an ideal gas The Maxwell-Boltzmann distribution of Let v x be the velocity component in the x direction of molecules having a mass m. All molecules located in the volume v x t A, and moving to the wall of area A, will strike the wall. If n is the number of molecules per unit volume, the number of molecules that will strike the wall in the time t will be 1/2n Av x t.
5 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Presure of an ideal gas The Maxwell-Boltzmann distribution of The force on the wall due to the colision of a molecule is F = d(mv)/dt, which yields F t = (mv). If molecules rebound elastically, (mv) = 2mv x. Therefore: F t = 2mv x. Consequently, for the total number of molecular colisions, F t = (1/2n Av x t)(2mv x ) p = F/A = n mv 2 x. If the motion of the gas is isotropic, then v 2 x = v 2 y = v 2 z = v 2 /3. therefore p = 1 3 n m v 2 Note that presure is proportional to v 2.
6 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Temperature and energy of an ideal gas The Maxwell-Boltzmann distribution of Using ɛ = m v 2 /2 and n = nn A /V, where N A is the Avogrado s number and n is the number of moles, the above equation for presure can be written as pv = 2nN A ɛ /3. Comparing this result with the empirical ideal gas law pv = nrt, and defining k as Boltzmann s constant k = R/N A, it is easy to conclude: T = pv nr = 2 N A 3 R ɛ ɛ = 3 2 kt v2 = 3 kt m
7 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Fundamental hypotheses The Maxwell-Boltzmann distribution of The distribution of molecular speeds we want to compute is F(v x, v y, v z )dv x dv y dv z, which gives us the probability of finding the x, y, z components of speed between v x and v x + dv x, v y and v y + dv y, v z and v z + dv z, respectively. 1 In each direction, the velocity distribution is an even funcion of v. 2 In any particular direction, the velocity distribution is independent and uncorrelated with the distributions in orthogonal directions. 3 The v 2 obtained from the distribution function should agree with v 2 = 3kT/m. 4 The three dimensional velocity distribution depends only on the speed v and not on the direction.
8 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Derivation of the distribution The Maxwell-Boltzmann distribution of hypothesis 1 The number of molecules moving in a given direction must be equal to the number of molecules moving in the oposite direction. (Otherwise, the presure on one side of the volume would be greater than on the other). Therefore, the distribution function should satisfy F(v x ) = F( v x ), F(v y ) = F( v y ), F(v z ) = F( v z ). one posibility is... F(v x ) = f (v 2 x) F(v y ) = f (v 2 y) F(v z ) = f (v 2 z )
9 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Derivation of the distribution The Maxwell-Boltzmann distribution of hypothesis 2 There should be no relationship between x axis, y axis, and z axis velocities. The three components of velocity should be independent. F(v x, v y, v z ) = F(v x )F(v y )F(v z ). From hypothesis 1, F(v x, v y, v z ) = f (v 2 x)f (v 2 y)f (v 2 z ). The only function that has the property f (a + b + c) = f (a) f (b) f (c) is the exponential function. ( κ ) 1/2 F(v x ) = f (v 2 x) = exp (±κv 2 π x ) ( κ ) 1/2 F(v y ) = f (v 2 y) = exp (±κv 2 π y ) ( κ ) 1/2 F(v z ) = f (v 2 z ) = exp (±κv 2 π z )
10 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Derivation of the distribution hypothesis 3 v 2 should agree with the ideal gas law: v 2 = 3kT/m. v 2 x = v 2 xf(v x )dv x = 1 2κ From v 2 = v 2 x + v 2 y + v 2 z = 3 v 2 x v 2 = 3/2κ. The Maxwell-Boltzmann distribution of 3 2κ = 3kT m κ = m 2kT F(v x, v y, v z ) dv x dv y dv z = F(v x )F(v y )F(v z ) dv x dv y dv z = ( m ) 3/2 mv 2 = exp ( 2πkT 2kT ) dv xdv y dv z
11 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Derivation of the distribution The Maxwell-Boltzmann distribution of hypothesis 4 From hypothesis 3, F(v x, v y, v z ) depends on v 2, not on the directional property of v. That is, it depends on the speed, not on the velocity. The probability that the speed is between v and v + dv is equal to the probability that velocity vectors terminate within the volume of a spherical shell between the radius v and the radius v + dv. Thus, dv x dv y dv z = 4πv 2 dv. Maxwell-Boltzmann distribution: ( F(v)dv = 4πv 2 m 2πkT ) 3/2 exp ( mv 2 2kT )dv
12 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Energy distribution The Maxwell-Boltzmann distribution of Note that our previous result is consistent with the Boltzmann distribution law, which states that the probability of finding a system with energy ɛ is proportional to exp ( ɛ/kt). This fact validates our choice F(v x ) = f (v 2 x). Taking into account that ɛ = mv 2 /2 and dɛ = mvdv = 2mɛdv, we can convert velocies to energies. Energy distribution: G(ɛ)dɛ = 4π ( ) 2ɛ ( m ) 3/2 ( exp ɛ ) dɛ = m 2πkT kt 2mɛ ( ) 1 3/2 ( = 2π ɛ exp ɛ ) dɛ πkt kt
13 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Molecular collisions. The Maxwell-Boltzmann distribution of Since two molecules must have a close encounter to react, the molecular collision rate provides an upper limit to the reaction rate. The molecular collision rate between two species depends on: 1 The average relative speed of the molecules of the different species, v r. 2 The size of the molecules of each species. 3 The number of possible collision pairs.
14 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Molecular collisions The Maxwell-Boltzmann distribution of The number of collisions one molecule of type 1 will experience with molecules of type 2 per unit time is Z 2 = πb 2 max v r n 2 Of course, for a molecule of type 1 moving through other molecules of the same type, Z 1 = πb 2 max v r n 1 = πd 2 v r n 1
15 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Molecular collisions The Maxwell-Boltzmann distribution of The total number of collisions of molecules of type 1 with those of type 2 per unit time and per unit volume is simply: Z 12 = Z 2 n 1 = πb 2 max v r n 1n 2 By a similiar argument, if there were only one type of molecule, the total number of collisions per unit time and per unit volume is: Z 11 = 1 2 Z 1n 1 = 1 2 πb2 max v r (n 1) 2 The factor 1/2 appears because, if there are n molecules, then the number of pairs is n(n 1)/2, which tends to n 2 /2 as n 1.
16 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Statistical Reactions mechanics Summary of gases Molecular collisions The Maxwell-Boltzmann distribution of How do we compute v r? Let us consider the average over all collision angles. The representative of the average angle of collision occurs when the molecules are traveling at right angles to one another. In this case (assuming equal masses for the particules), the relative velocity will have a magnitude of v r = 2 v. On the other hand v = v r = 2 v = 0 vf(v)dv = ( ) 8kT 1/2 = π(m/2) The last term is also the general solution. ( ) 8kT 1/2 πm ( ) 8kT 1/2 πµ
17 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Introduction Chemical reactions are described both at a macroscopic level and a microcospic level. At macroscopic level, the goal is to obtain an empirical description of the rates of the chemical reactions. Experiments tell us that these rates depend on: 1 the temperature, presure, and volume of the reaction vessel 2 the concentrations of the reactants and products 3 whether or not a catalyst is present At microcospic level, the goal is to understand the physics and dynamics of the reaction. Theories of chemical reactions attempt to obtain the macroscopic reaction rates and relate them with underlying mechanisms that govern the reaction at microscopic level.
18 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Differential laws aa + bb cc + dd Since 1 d[c] = 1 d[d] = 1 d[a] = 1 d[b], c dt d dt a dt b dt the rate of a reaction is defined as the rate of change of the concentration of a product or reactant over its stoichiometric number. The rate law for a reaction can therefore be written as, for instance, 1 d[c] = f ([A(t)], [B(t)], [C(t)], [D(t)]). c dt
19 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Differential laws In general, the function f ([A], [B], [C], [D]) might be a complicated function of the concentrations. However, it often occurs that f can be expressed as a simple product of a rate constant k, and the concentrations each raised to some power: 1 d[c] = k[a] m [B] n [C] o [D] p c dt When the rate law can be written in this simple way, the overall order of the reaction is defined as q = m + n + o + p the order respect to a particular species is defined as the power to which its concentration is raised.
20 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Differential laws important notes 1 d[c] = k[a] m [B] n [C] o [D] p c dt The left-hand side of the above equation has units of concentration per time, the rate constant k will then have units of time 1 concentration q. The overall order of a reaction cannot be obtained simply by looking at the overall stoichiometric numbers. It is determined experimentally. Example: however, its reaction rate is H 2 + Br 2 2HBr 1 d[hbr] = k[h 2 ][Br 2 ] 1/2 2 dt
21 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Integrated laws The rate law in its differential form describes how the rate of the reaction depends on the concentrations. integration It is often useful to determine how the concentrations themselves vary in time. This variation in time is computed by direct integration of the differential rate law. To do the integration, one needs to know the order of the reation. Only for simple reaction orders is the integration straitforward.
22 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Examples of integrated laws First-order reactions. A products d[a] dt = k[a] [A(t)] = [A(0)] exp ( kt) Second-order reaction. 2A products d[a] dt = k[a] 2 1 [A(t)] 1 [A(0)] = kt Second-order reaction. A + B products d[a] dt = k[a][b] ln [B(t)][A(0)] = ([B(0)] [A(0)])kt [B(0)][A(t)]
23 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Elementary steps postulate The macroscopic rate law is the consequence of a mechanism consisting of elementary steps, each one of which describes a process that takes place on the microscopic level. Three types of microscopic processes account for essentially all reaction mechanisms: unimolecular process: reaction of a single (energized) molecule. A products. Since the number of product molecules produced per unit time is proportional to the number of A molecules, then d[products] dt = d[a] dt = k[a]
24 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Elementary steps postulate Three types of microscopic processes account for essentially all reaction mechanisms: bimolecular process: collision between two molecular species. A + B products. Since the number of products per unit time is proportional to the number of collisions between A and B, then d[products] dt = k[a][b] termolecular process: collision between three molecular species. A + B + C products. Since the number of products per unit time is proportional to the number of collisions between A, B, and C, then d[products] = k[a][b][c] dt
25 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Elementary steps postulate Therefore, unimolecular processes follow first-order kinetics, biomolecular processes follow second-order kinetics, and termolecular processes follow third-order kinetics. The order of an elementary process is thus equal to its molecularity. This statement is only true for elementary processes, not necessarily for an overall process consisting of several elementary steps.
26 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Example of chemical reaction as combination of elementary reactions H 2 + Br 2 2HBr It has been shown that this reaction is what it is usually called a chain mechanism, which in this case consists of collisional production of Br atoms (fast): Br 2 + M 2Br + M Br + H 2 HBr + H H + HBr Br + H 2 H + Br 2 HBr + Br (slow reaction) (slow reaction) (fast reaction)
27 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Unimolecular decomposition (A products): The Lindemann mechanism How does a A molecule obtain enough energy to decompose? Lindemann suggested A + M A + M A products where M represents any molecule that can energize A by collision. (M might be A itself, or it might be a nonreactive molecule in which the reactant is mixed). The overall rate of the reaction is d[p]/dt = k 2 [A ]. The existence of the intermediate A complicates the quantitative solution substancially.
28 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Differential Reactions andsummary integrated laws Reactions mechanisms Important typ Enzyme catalysis: The Michaelis-Menten mechanism Enzymes tend to speed up chemical reactions E + S X X products + E where X represents an intermediate and S is called the substrate.
29 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Collision Reactions theorysummary Activated complex theory Collision theory remember The rate of molecular collisions provides an upper limit to the reaction rate, since two molecules have to come close to react. Z 12 = Z 2 n 1 = πb 2 max v r n 1n 2 however Not all collisions will lead to reaction. It is supposed that reactions take place if the relative energy of the collision (corresponding to a relative velocity v r ) is sufficiently large, larger than a particular value ɛ. πb 2 max is the cross section for hard-sphere collisions. From the above discussion, however, the cross section should depend on the relative energy. Let us denote it as σ(ɛ r ).
30 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Collision Reactions theorysummary Activated complex theory Collision theory therefore The number of collisions between molecules of type 1 and type 2 can be written as Z 12 = k(ɛ r ) n 1n 2 where k(ɛ r ) = σ(ɛ r )v r is the rate constant for the reaction at ɛ r = µv 2 r /2. From v r = 2ɛ r /µ and ( ) 1 3/2 ( G(ɛ r )dɛ r = 2π ɛr exp ɛ ) r dɛ r, πkt kt we can compute k(t) = k(ɛ r ) = σ(ɛ r )v r G(ɛ r )dɛ r =
31 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Collision Reactions theorysummary Activated complex theory Collision theory result k(t) = A ( ) 8kT 1/2 exp ( ɛ πµ kt ) remarks Although this expression accounts only for the relative translational energy of the reactants, it is possible to arrive to the same expression when the internal vibrational energy is also considered. This expression is very similar to the Arrhenius form k = A exp ( E a kt ) Reactants have favorable orientations for reaction. ( ) 8kT 1/2 k(t) = pa exp ( ɛ πµ kt )
32 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Collision Reactions theorysummary Activated complex theory Activated complex theory result A theory that improves on the simple collision model by incorporating into the theory the partitions functions that describe the number of states accessible at the temperature of interest. It starts by modeling a chemical reaction by A + B AB products k(t) = kt h q q a q b exp ( ɛ kt ) where q is the partition function per unit volume for the activated complex, and q a and q b are the partition functions per unit volume for the reactants.
33 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Reactions Summary Summary Statistical mechanics is the basic toolbox that is used to model chemical kinetics. Depending on the hypothesis considered, different models might be constructed to model the same chemical system. Also, for chemical systems with different structural features, different statistical hypotheses will need to be considered. Consequently, different models might be constructed, depending on the systems. The main function of these models is to related the empirical, macroscopic description of the chemical reactions with the underlying mechanisms for the reactions on the microscopic level.
34 Kinetic Theory of Gases Rates of Chemical Reactions Theories of Chemical Reactions Summary Acknowledgment PROYECTO PROMETEO Secretaría de Educación Superior Ciencia, Tecnología, e Innovación de la República del Ecuador Escuela Politécnica Nacional Proyecto Prometeo
Reaction time distributions in chemical kinetics: Oscillations and other weird behaviors
Introduction The algorithm Results Summary Reaction time distributions in chemical kinetics: Oscillations and other weird behaviors Ramon Xulvi-Brunet Escuela Politécnica Nacional Outline Introduction
More informationRate Laws. many elementary reactions. The overall stoichiometry of a composite reaction tells us little about the mechanism!
Rate Laws We have seen how to obtain the differential form of rate laws based upon experimental observation. As they involve derivatives, we must integrate the rate equations to obtain the time dependence
More informationChemical Kinetics. Chapter 13. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chemical Kinetics Chapter 13 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chemical Kinetics Thermodynamics does a reaction take place? Kinetics how fast does
More informationAdvanced Physical Chemistry CHAPTER 18 ELEMENTARY CHEMICAL KINETICS
Experimental Kinetics and Gas Phase Reactions Advanced Physical Chemistry CHAPTER 18 ELEMENTARY CHEMICAL KINETICS Professor Angelo R. Rossi http://homepages.uconn.edu/rossi Department of Chemistry, Room
More informationChemical Kinetics AP Chemistry Lecture Outline
Chemical Kinetics AP Chemistry Lecture Outline Name: Factors that govern rates of reactions. Generally... (1)...as the concentration of reactants increases, rate (2)...as temperature increases, rate (3)...with
More informationChemical Kinetics. Rate = [B] t. Rate = [A] t. Chapter 12. Reaction Rates 01. Reaction Rates 02. Reaction Rates 03
Chapter Chemical Kinetics Reaction Rates 0 Reaction Rate: The change in the concentration of a reactant or a product with time (M/s). Reactant Products aa bb Rate = [A] t Rate = [B] t Reaction Rates 0
More information1. Introduction to Chemical Kinetics
1. Introduction to Chemical Kinetics objectives of chemical kinetics 1) Determine empirical rate laws H 2 + I 2 2HI How does the concentration of H 2, I 2, and HI change with time? 2) Determine the mechanism
More informationChapter 12. Chemical Kinetics
Chapter 12 Chemical Kinetics Chapter 12 Table of Contents 12.1 Reaction Rates 12.2 Rate Laws: An Introduction 12.3 Determining the Form of the Rate Law 12.4 The Integrated Rate Law 12.5 Reaction Mechanisms
More informationCh 13 Rates of Reaction (Chemical Kinetics)
Ch 13 Rates of Reaction (Chemical Kinetics) Reaction Rates and Kinetics - The reaction rate is how fast reactants are converted to products. - Chemical kinetics is the study of reaction rates. Kinetics
More informationAP Chemistry - Notes - Chapter 12 - Kinetics Page 1 of 7 Chapter 12 outline : Chemical kinetics
AP Chemistry - Notes - Chapter 12 - Kinetics Page 1 of 7 Chapter 12 outline : Chemical kinetics A. Chemical Kinetics - chemistry of reaction rates 1. Reaction Rates a. Reaction rate- the change in concentration
More informationChemical Kinetics. Topic 7
Chemical Kinetics Topic 7 Corrosion of Titanic wrec Casón shipwrec 2Fe(s) + 3/2O 2 (g) + H 2 O --> Fe 2 O 3.H 2 O(s) 2Na(s) + 2H 2 O --> 2NaOH(aq) + H 2 (g) Two examples of the time needed for a chemical
More informationKinetic Model of Gases
Kinetic Model of Gases Section 1.3 of Atkins, 6th Ed, 24.1 of Atkins, 7th Ed. 21.1 of Atkins, 8th Ed., and 20.1 of Atkins, 9th Ed. Basic Assumptions Molecular Speeds RMS Speed Maxwell Distribution of Speeds
More informationChemical Kinetics Ch t ap 1 er
Chemical Kinetics Chapter 13 1 Chemical Kinetics Thermodynamics does a reaction take place? Kinetics how fast does a reaction proceed? Reaction rate is the change in the concentration of a reactant or
More informationElementary Reactions
Elementary Reactions Elementary reactions occur in a single encounter Unimolecular: A Rate = k[a] Bimolecular: A + B Rate = k[a][b] Termolecular: A + B + C Rate = k[a][b][c] Termolecular reactions are
More informationTOPIC 6: Chemical kinetics
TOPIC 6: Chemical kinetics Reaction rates Reaction rate laws Integrated reaction rate laws Reaction mechanism Kinetic theories Arrhenius law Catalysis Enzimatic catalysis Fuente: Cedre http://loincognito.-iles.wordpress.com/202/04/titanic-
More informationChapter 18 Thermal Properties of Matter
Chapter 18 Thermal Properties of Matter In this section we define the thermodynamic state variables and their relationship to each other, called the equation of state. The system of interest (most of the
More informationCh 13 Chemical Kinetics. Modified by Dr. Cheng-Yu Lai
Ch 13 Chemical Kinetics Modified by Dr. Cheng-Yu Lai Outline 1. Meaning of reaction rate 2. Reaction rate and concentration 3. Writing a Rate Law 4. Reactant concentration and time 5. Reaction rate and
More informationChapter 12. Chemical Kinetics
Chapter 12 Chemical Kinetics Section 12.1 Reaction Rates Section 12.1 Reaction Rates Section 12.1 Reaction Rates Section 12.1 Reaction Rates Section 12.1 Reaction Rates Section 12.1 Reaction Rates Section
More informationName: UNIT 5 KINETICS NOTES PACEKT #: KINETICS NOTES PART C
KINETICS NOTES PART C IV) Section 14.4 The Change of Concentration with Time A) Integrated Rate Law: shows how the concentration of the reactant(s) varies with time 1) [A]0 is the initial concentration
More informationCh. 19: The Kinetic Theory of Gases
Ch. 19: The Kinetic Theory of Gases In this chapter we consider the physics of gases. If the atoms or molecules that make up a gas collide with the walls of their container, they exert a pressure p on
More informationHow fast reactants turn into products. Usually measured in Molarity per second units. Kinetics
How fast reactants turn into products. Usually measured in Molarity per second units. Kinetics Reaction rated are fractions of a second for fireworks to explode. Reaction Rates takes years for a metal
More informationChemical Kinetics. Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chemical Kinetics Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chemical Kinetics Thermodynamics does a reaction take place? Kinetics how fast does a reaction
More informationChapter 12. Chemical Kinetics
Chapter 12 Chemical Kinetics Section 12.1 Reaction Rates Reaction Rate Change in concentration of a reactant or product per unit time. Rate = concentration of A at time t t 2 1 2 1 concentration of A at
More informationChapter 11: CHEMICAL KINETICS
Chapter : CHEMICAL KINETICS Study of the rate of a chemical reaction. Reaction Rate (fast or slow?) Igniting gasoline? Making of oil? Iron rusting? We know about speed (miles/hr). Speed Rate = changes
More information11/9/2012 CHEMICAL REACTIONS. 1. Will the reaction occur? 2. How far will the reaction proceed? 3. How fast will the reaction occur?
CHEMICAL REACTIONS LECTURE 11: CHEMICAL KINETICS 1. Will the reaction occur? 2. How far will the reaction proceed? 3. How fast will the reaction occur? CHEMICAL REACTIONS C(s, diamond) C(s, graphite) G
More informationChapter 14 Kinetic Theory
Chapter 14 Kinetic Theory Kinetic Theory of Gases A remarkable triumph of molecular theory was showing that the macroscopic properties of an ideal gas are related to the molecular properties. This is the
More informationCHAPTER 13 (MOORE) CHEMICAL KINETICS: RATES AND MECHANISMS OF CHEMICAL REACTIONS
CHAPTER 13 (MOORE) CHEMICAL KINETICS: RATES AND MECHANISMS OF CHEMICAL REACTIONS This chapter deals with reaction rates, or how fast chemical reactions occur. Reaction rates vary greatly some are very
More informationPart One: Reaction Rates. 1. Even though a reaction is thermodynamically favorable it may not occur at all if it is kinetically very slow.
CHAPTER 13: RATES OF REACTION Part One: Reaction Rates A. Chemical Kinetics deals with: 1. 2. B. Importance: 1. Even though a reaction is thermodynamically favorable it may not occur at all if it is kinetically
More informationKinetics. Chapter 14. Chemical Kinetics
Lecture Presentation Chapter 14 Yonsei University In kinetics we study the rate at which a chemical process occurs. Besides information about the speed at which reactions occur, kinetics also sheds light
More information= dc A dt. The above is a bimolecular elementary reaction. A unimolecular elementary reaction might be HO 2 H + O 2
The above is a bimolecular elementary reaction. A unimolecular elementary reaction might be HO 2 H + O 2 HO 2 just dissociates without any other influence. Rate Laws for Elementary Reactions: 1) A Fragments,
More informationC H E M I C N E S C I
C H E M I C A L K I N E T S C I 4. Chemical Kinetics Introduction Average and instantaneous Rate of a reaction Express the rate of a reaction in terms of change in concentration Elementary and Complex
More informationε tran ε tran = nrt = 2 3 N ε tran = 2 3 nn A ε tran nn A nr ε tran = 2 N A i.e. T = R ε tran = 2
F1 (a) Since the ideal gas equation of state is PV = nrt, we can equate the right-hand sides of both these equations (i.e. with PV = 2 3 N ε tran )and write: nrt = 2 3 N ε tran = 2 3 nn A ε tran i.e. T
More informationChapter 11 Rate of Reaction
William L Masterton Cecile N. Hurley http://academic.cengage.com/chemistry/masterton Chapter 11 Rate of Reaction Edward J. Neth University of Connecticut Outline 1. Meaning of reaction rate 2. Reaction
More informationPart One: Reaction Rates. 1. Rates of chemical reactions. (how fast products are formed and/or reactants are used up)
A. Chemical Kinetics deals with: CHAPTER 13: RATES OF REACTION Part One: Reaction Rates 1. Rates of chemical reactions. (how fast products are formed and/or reactants are used up) 2. Mechanisms of chemical
More informationPlug flow Steady-state flow. Mixed flow
1 IDEAL REACTOR TYPES Batch Plug flow Steady-state flow Mixed flow Ideal Batch Reactor It has neither inflow nor outflow of reactants or products when the reaction is being carried out. Uniform composition
More informationREACTION KINETICS. Catalysts substances that increase the rates of chemical reactions without being used up. e.g. enzymes.
REACTION KINETICS Study of reaction rates Why? Rates of chemical reactions are primarily controlled by 5 factors: the chemical nature of the reactants 2 the ability of the reactants to come in contact
More informationBrown et al, Chemistry, 2nd ed (AUS), Ch. 12:
Kinetics: Contents Brown et al, Chemistry, 2 nd ed (AUS), Ch. 12: Why kinetics? What is kinetics? Factors that Affect Reaction Rates Reaction Rates Concentration and Reaction Rate The Change of Concentration
More informationCY T. Pradeep. Lectures 11 Theories of Reaction Rates
CY1001 2015 T. Pradeep Lectures 11 Theories of Reaction Rates There are two basic theories: Collision theory and activated complex theory (transition state theory). Simplest is the collision theory accounts
More informationCHM 5423 Atmospheric Chemistry Notes on kinetics (Chapter 4)
CHM 5423 Atmospheric Chemistry Notes on kinetics (Chapter 4) Introduction A mechanism is one or a series of elementary reactions that convert reactants into products or otherwise model the chemistry of
More informationCHEMISTRY. Chapter 14 Chemical Kinetics
CHEMISTRY The Central Science 8 th Edition Chapter 14 Kozet YAPSAKLI kinetics is the study of how rapidly chemical reactions occur. rate at which a chemical process occurs. Reaction rates depends on The
More informationChapter 14 Chemical Kinetics
7/10/003 Chapter 14 Chemical Kinetics 14-1 Rates of Chemical Reactions 14- Reaction Rates and Concentrations 14-3 The Dependence of Concentrations on Time 14-4 Reaction Mechanisms 14-5 Reaction Mechanism
More informationName AP CHEM / / Chapter 12 Outline Chemical Kinetics
Name AP CHEM / / Chapter 12 Outline Chemical Kinetics The area of chemistry that deals with the rate at which reactions occur is called chemical kinetics. One of the goals of chemical kinetics is to understand
More informationKinetic Theory of Gases
Kinetic Theory of Gases Chapter 3 P. J. Grandinetti Chem. 4300 Aug. 28, 2017 P. J. Grandinetti (Chem. 4300) Kinetic Theory of Gases Aug. 28, 2017 1 / 45 History of ideal gas law 1662: Robert Boyle discovered
More informationChapter 13 Kinetics: Rates and Mechanisms of Chemical Reactions
Chapter 13 Kinetics: Rates and Mechanisms of Chemical Reactions 14.1 Focusing on Reaction Rate 14.2 Expressing the Reaction Rate 14.3 The Rate Law and Its Components 14.4 Integrated Rate Laws: Concentration
More informationReaction Rate. Rate = Conc. of A at t 2 -Conc. of A at t 1. t 2 -t 1. Rate = Δ[A] Δt
Kinetics The study of reaction rates. Spontaneous reactions are reactions that will happen - but we can t tell how fast. Diamond will spontaneously turn to graphite eventually. Reaction mechanism- the
More informationOutline: Kinetics. Reaction Rates. Rate Laws. Integrated Rate Laws. Half-life. Arrhenius Equation How rate constant changes with T.
Chemical Kinetics Kinetics Studies the rate at which a chemical process occurs. Besides information about the speed at which reactions occur, kinetics also sheds light on the reaction mechanism (exactly
More informationCHAPTER 9 LECTURE NOTES
CHAPTER 9 LECTURE NOTES 9.1, 9.2: Rate of a reaction For a general reaction of the type A + 3B 2Y, the rates of consumption of A and B, and the rate of formation of Y are defined as follows: Rate of consumption
More information2 Reaction kinetics in gases
2 Reaction kinetics in gases October 8, 2014 In a reaction between two species, for example a fuel and an oxidizer, bonds are broken up and new are established in the collision between the species. In
More informationGeneral Chemistry I Concepts
Chemical Kinetics Chemical Kinetics The Rate of a Reaction (14.1) The Rate Law (14.2) Relation Between Reactant Concentration and Time (14.3) Activation Energy and Temperature Dependence of Rate Constants
More informationChapter 14 Chemical Kinetics
4//004 Chapter 4 Chemical Kinetics 4- Rates of Chemical Reactions 4- Reaction Rates and Concentrations 4-3 The Dependence of Concentrations on Time 4-4 Reaction Mechanisms 4-5 Reaction Mechanism and Rate
More informationThe Rate Expression. The rate, velocity, or speed of a reaction
The Rate Expression The rate, velocity, or speed of a reaction Reaction rate is the change in the concentration of a reactant or a product with time. A B rate = - da rate = db da = decrease in concentration
More informationELEMENTARY CHEMICAL KINETICS
ELEMENTARY CHEMICAL KINETICS EDR Chapter 25... a knowledge of the rate, or time dependence, of chemical change is of critical importance for the successful synthesis of new materials and for the utilization
More informationThe Kinetic Theory of Gases (1)
Chapter 4 The Kinetic Theory of Gases () Topics Motivation and assumptions for a kinetic theory of gases Joule expansion The role of collisions Probabilities and how to combine them The velocity distribution
More informationChemical Kinetics and Equilibrium
Chemical Kinetics and Equilibrium Part 1: Kinetics David A. Katz Department of Chemistry Pima Community College Tucson, AZ USA Chemical Kinetics The study of the rates of chemical reactions and how they
More information14.1 Expressing the Reaction Rate
14.1 Expressing the Reaction Rate Differential Rate and Integrated Rate Laws Fred Omega Garces Chemistry 201 Miramar College 1 Expressing Reaction Rates Outline Kinetics: Intro Factors influencing Reaction
More informationKinetic theory of the ideal gas
Appendix H Kinetic theory of the ideal gas This Appendix contains sketchy notes, summarizing the main results of elementary kinetic theory. The students who are not familiar with these topics should refer
More informationChapter 14: Chemical Kinetics
C h e m i c a l K i n e t i c s P a g e 1 Chapter 14: Chemical Kinetics Homework: Read Chapter 14 Work out sample/practice exercises in the sections, Check for the MasteringChemistry.com assignment and
More informationTheoretical Models for Chemical Kinetics
Theoretical Models for Chemical Kinetics Thus far we have calculated rate laws, rate constants, reaction orders, etc. based on observations of macroscopic properties, but what is happening at the molecular
More informationCHEMISTRY NOTES CHEMICAL KINETICS
CHEMICAL KINETICS Rate of chemical reactions The rate of a reaction tells us how fast the reaction occurs. Let us consider a simple reaction. A + B C + D As the reaction proceeds, the concentration of
More informationExpress the transition state equilibrium constant in terms of the partition functions of the transition state and the
Module 7 : Theories of Reaction Rates Lecture 33 : Transition State Theory Objectives After studying this Lecture you will be able to do the following. Distinguish between collision theory and transition
More informationModule 6 : Reaction Kinetics and Dynamics Lecture 28 : Elementary Reactions and Reaction Mechanisms
Module 6 : Reaction Kinetics and Dynamics Lecture 28 : Elementary Reactions and Reaction Mechanisms Objectives In this Lecture you will learn to do the following Define what is an elementary reaction.
More informationKinetic Theory of Gases
EDR = Engel, Drobny, Reid, Physical Chemistry for the Life Sciences text Kinetic Theory of Gases Levine Chapter 14 "So many of the properties of [gases]...can be deduced from the hypothesis that their
More informationChapter 14 Chemical Kinetics
Chapter 14 Chemical Kinetics Learning goals and key skills: Understand the factors that affect the rate of chemical reactions Determine the rate of reaction given time and concentration Relate the rate
More informationLecture Presentation. Chapter 14. Chemical Kinetics. John D. Bookstaver St. Charles Community College Cottleville, MO Pearson Education, Inc.
Lecture Presentation Chapter 14 John D. Bookstaver St. Charles Community College Cottleville, MO In kinetics we study the rate at which a chemical process occurs. Besides information about the speed at
More informationCalculating Rates of Substances. Rates of Substances. Ch. 12: Kinetics 12/14/2017. Creative Commons License
Ch. 2: Kinetics An agama lizard basks in the sun. As its body warms, the chemical reactions of its metabolism speed up. Chemistry: OpenStax Creative Commons License Images and tables in this file have
More information11/2/ and the not so familiar. Chemical kinetics is the study of how fast reactions take place.
Familiar Kinetics...and the not so familiar Reaction Rates Chemical kinetics is the study of how fast reactions take place. Some happen almost instantaneously, while others can take millions of years.
More informationLecture Presentation. Chapter 14. James F. Kirby Quinnipiac University Hamden, CT. Chemical Kinetics Pearson Education, Inc.
Lecture Presentation Chapter 14 James F. Kirby Quinnipiac University Hamden, CT In chemical kinetics we study the rate (or speed) at which a chemical process occurs. Besides information about the speed
More informationWhat we learn from Chap. 15
Chemical Kinetics Chapter 15 What we learn from Chap. 15 15. The focus of this chapter is the rates and mechanisms of chemical reactions. The applications center around pesticides, beginning with the opening
More informationChemical. Chapter 14. Kinetics. Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E.
Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Chapter 14 1 PDF Created with deskpdf PDF www.farq.xyz Writer - Trial :: http://www.docudesk.com
More informationAP CHEMISTRY NOTES 7-1 KINETICS AND RATE LAW AN INTRODUCTION
AP CHEMISTRY NOTES 7-1 KINETICS AND RATE LAW AN INTRODUCTION CHEMICAL KINETICS the study of rates of chemical reactions and the mechanisms by which they occur FACTORS WHICH AFFECT REACTION RATES 1. Nature
More informationChapter 30. Chemical Kinetics. Copyright (c) 2011 by Michael A. Janusa, PhD. All rights reserved.
Chapter 30 Chemical Kinetics 1 Copyright (c) 2011 by Michael A. Janusa, PhD. All rights reserved. Chemists have three fundamental questions in mind when they study chemical reactions: 1.) What happens?
More informationExamples of fast and slow reactions
1 of 10 After completing this chapter, you should, at a minimum, be able to do the following. This information can be found in my lecture notes for this and other chapters and also in your text. Correctly
More informationKinetics - Chapter 14. reactions are reactions that will happen - but we can t tell how fast. - the steps by which a reaction takes place.
The study of. Kinetics - Chapter 14 reactions are reactions that will happen - but we can t tell how fast. - the steps by which a reaction takes place. Factors that Affect Rx Rates 1. The more readily
More informationChapter 14 Chemical Kinetics
Chapter 14 Chemical Kinetics Factors that Affect Reaction rates Reaction Rates Concentration and Rate The Change of Concentration with Time Temperature and Rate Reactions Mechanisms Catalysis Chemical
More informationCHAPTER 10 CHEMICAL KINETICS
CHAPTER 10 CHEMICAL KINETICS Introduction To this point in our study of chemistry, we have been concerned only with the composition of the equilibrium mixture, not the length of time required to obtain
More informationFactors That Affect Rates. Factors That Affect Rates. Factors That Affect Rates. Factors That Affect Rates
KINETICS Kinetics Study of the speed or rate of a reaction under various conditions Thermodynamically favorable reactions DO NOT mean fast reactions Some reactions take fraction of a second (explosion)
More informationChapter 15 Thermal Properties of Matter
Chapter 15 Thermal Properties of Matter To understand the mole and Avogadro's number. To understand equations of state. To study the kinetic theory of ideal gas. To understand heat capacity. To learn and
More informationChapter 14 Chemical Kinetics
Chapter 14 14.1 Factors that Affect Reaction Rates 14.2 Reaction Rates 14.3 Concentration and Rate Laws 14.4 The Change of Concentration with Time 14.5 Temperature and Rate 14.6 Reaction Mechanisms 14.7
More informationChemical Reaction Engineering. Lecture 2
hemical Reaction Engineering Lecture 2 General algorithm of hemical Reaction Engineering Mole balance Rate laws Stoichiometry Energy balance ombine and Solve lassification of reactions Phases involved:
More informationCollision Theory and Rate of Reaction. Sunday, April 15, 18
Collision Theory and Rate of Reaction Collision Theory System consists of particles in constant motion at speed proportional to temperature of sample Chemical reaction must involve collisions of particles
More informationThis is a statistical treatment of the large ensemble of molecules that make up a gas. We had expressed the ideal gas law as: pv = nrt (1)
1. Kinetic Theory of Gases This is a statistical treatment of the large ensemble of molecules that make up a gas. We had expressed the ideal gas law as: pv = nrt (1) where n is the number of moles. We
More informationKinetics. Mary J. Bojan Chem Rate: change that occurs in a given interval of time.
Kinetics Rates of reaction average rates instantaneous rates Dependence of rate on concentration rate constant rate laws order of the reaction Dependence of rate on time First order Second order Half-life
More informationAP CHEMISTRY CHAPTER 12 KINETICS
AP CHEMISTRY CHAPTER 12 KINETICS Thermodynamics tells us if a reaction can occur. Kinetics tells us how quickly the reaction occurs. Some reactions that are thermodynamically feasible are kinetically so
More informationIntroduction to Chemical Kinetics. Chemical Kinetics
Introduction to Chemical Kinetics CHEM 102 T. Hughbanks Chemical Kinetics Reaction rates How fast? Reaction mechanisms How? Answers to these questions depend on the path taken from reactants to products.
More informationLecture 27. Transition States and Enzyme Catalysis
Lecture 27 Transition States and Enzyme Catalysis Reading for Today: Chapter 15 sections B and C Chapter 16 next two lectures 4/8/16 1 Pop Question 9 Binding data for your thesis protein (YTP), binding
More informationBIO134: Chemical Kinetics
BIO134: Chemical Kinetics K Ando School of Chemistry, University of Birmingham http://www.chem.bham.ac.uk/labs/ando/bio134/ Last updated: February 18, 2005 Contents 1 Thermodynamics 3 1.1 The 1st and 2nd
More informationFoundations of Chemical Kinetics. Lecture 17: Unimolecular reactions in the gas phase: Lindemann-Hinshelwood theory
Foundations of Chemical Kinetics Lecture 17: Unimolecular reactions in the gas phase: Lindemann-Hinshelwood theory Marc R. Roussel Department of Chemistry and Biochemistry The factorial The number n(n
More informationPV = n R T = N k T. Measured from Vacuum = 0 Gauge Pressure = Vacuum - Atmospheric Atmospheric = 14.7 lbs/sq in = 10 5 N/m
PV = n R T = N k T P is the Absolute pressure Measured from Vacuum = 0 Gauge Pressure = Vacuum - Atmospheric Atmospheric = 14.7 lbs/sq in = 10 5 N/m V is the volume of the system in m 3 often the system
More informationChapter 12 - Chemical Kinetics
Chapter 1 - Chemical Kinetics 1.1 Reaction Rates A. Chemical kinetics 1. Study of the speed with which reactants are converted to products B. Reaction Rate 1. The change in concentration of a reactant
More informationPHEN 612 SPRING 2008 WEEK 1 LAURENT SIMON
PHEN 612 SPRING 2008 WEEK 1 LAURENT SIMON Chapter 1 * 1.1 Rate of reactions r A A+B->C Species A, B, and C We are interested in the rate of disappearance of A The rate of reaction, ra, is the number of
More informationlet: rate constant at sea level be ks and that on mountain be km ks/km = 100 ( 3mins as opposed to 300 mins)
homework solution : "egg question" let: rate constant at sea level be ks and that on mountain be km ks/km = 100 ( 3mins as opposed to 300 mins) ln ks/km = Ea x 10 / 373 x 363 x 8.314 x 10-3 4.605 = 10Ea/1125.7
More informationCHEM Dr. Babb s Sections Lecture Problem Sheets
CHEM 116 - Dr. Babb s Sections Lecture Problem Sheets Kinetics: Integrated Form of Rate Law 61. Give the integrated form of a zeroth order reaction. Define the half-life and find the halflife for a general
More informationElementary Reactions: these are hypothetical constructs, or our guess about how reactants are converted to products.
Mechanism Concept 1) Exponents in rate law do not depend on stoichiometric coefficients in chemical reactions. 2)What is the detailed way in which the reactants are converted into products? This is not
More informationChapter: Chemical Kinetics
Chapter: Chemical Kinetics Rate of Chemical Reaction Question 1 Nitrogen pentaoxide decomposes according to equation: This first order reaction was allowed to proceed at 40 o C and the data below were
More informationChemical kinetics and catalysis
Chemical kinetics and catalysis Outline Classification of chemical reactions Definition of chemical kinetics Rate of chemical reaction The law of chemical raction rate Collision theory of reactions, transition
More informationChapter 14. Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
Chemistry, The Central Science, 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten Chapter 14 John D. Bookstaver St. Charles Community College St. Peters, MO 2006, Prentice Hall,
More informationCHEMISTRY - CLUTCH CH.13 - CHEMICAL KINETICS.
!! www.clutchprep.com CONCEPT: RATES OF CHEMICAL REACTIONS is the study of reaction rates, and tells us the change in concentrations of reactants or products over a period of time. Although a chemical
More informationChapter 14: Chemical Kinetics II. Chem 102 Dr. Eloranta
Chapter 14: Chemical Kinetics II Chem 102 Dr. Eloranta Rate Laws If you are familiar with calculus Experiments would allow you to determine the reaction order and rate constant, but what if you wanted
More informationChemical Kinetics. Kinetics is the study of how fast chemical reactions occur. There are 4 important factors which affect rates of reactions:
Chemical Kinetics Kinetics is the study of how fast chemical reactions occur. There are 4 important factors which affect rates of reactions: reactant concentration temperature action of catalysts surface
More informationor more general example: aa + bb cc + dd r = -1/a da/dt = -1/b db/dt = 1/c dc/dt = 1/d dd/dt
Chem 344--Physical Chemistry for Biochemists II --F'12 I. Introduction see syllabus II. Experimental Chemical kinetics (Atkins, Ch.6) How fast is reaction? Rate of formation of product or loss of reactant
More information