1 Reaction Mechanisms: Reaction is broken into steps with intermediates being formed. “some RXNS occur in one step, but most occur in in multiple steps.”

Slides:

Advertisements

Similar presentations

Chemical Kinetics Reaction rate - the change in concentration of reactant or product per unit time.

Advertisements

Kinetics: Rates and Mechanisms of Reactions

Chapter 14 Chemical Kinetics.

Prentice Hall © 2003Chapter 14 Chapter 14 Chemical Kinetics CHEMISTRY The Central Science 9th Edition David P. White.

1 Kinetics Chapter The study of rxn rates Rxn rate =  concentration/  time Rxn rate =  concentration/  time Example: Example: 2N 2 O 5  4NO.

Section 14.6 Reaction Mechanisms and Catalysis

Chemistry 1011 Slot 51 Chemistry 1011 TOPIC Rate of Reaction TEXT REFERENCE Masterton and Hurley Chapter 11.

Topic 16 – Kinetics 16.2 – Reaction Mechanism IB Chemistry T16D07.

Chemical Kinetics Collision Theory: How reactions takes place

Explain that reactions can occur by more than one step and that the slowest step determines the rate of the reaction (rate- determining step)

© University of South Carolina Board of Trustees Chapt. 13 Sec. 6 Reaction Mechanisms.

Chemical Kinetics Rates of chemical reactions and how they can be measured experimentally and described mathematically.

Chemical Kinetics Chapter 15 H 2 O 2 decomposition in an insect H 2 O 2 decomposition catalyzed by MnO 2.

Outline:1/31/07 n n Turn in Research Symposium Seminar reports – to me n n Exam 1 – two weeks from Friday… n Today: Start Chapter 15: Kinetics Kinetics.

Chapter 14 Chemical Kinetics. What does ‘kinetics’ mean?

Chapter 15 Rates of Reaction.

 Some reactions are not represented in the reaction equation; such as, -Absorbing light energy -Colliding to the walls of the container  Many reactions.

Chapter 14.  Physical state of reactants:  Reactants must come in contact with one another in order for a reaction to occur.  Concentration of reactants:

Chemical Kinetics CHAPTER 14 Chemistry: The Molecular Nature of Matter, 6 th edition By Jesperson, Brady, & Hyslop.

Unit 6: Kinetics IB Topics 6 & 16 Part 3: Reaction Mechanisms & Activation Energy.

1 Chemical Kinetics The area of chemistry that concerns reaction rates. The area of chemistry that concerns reaction rates.

Reaction Mechanisms. Chemical Reactions  Glycolosis  C 6 H 12 O NAD ADP + 2 P  2 CH 3 COCOOH + 2 ATP + 2 NADH + 2 H +  This is the way.

Chemical Kinetics Rates of Reactions ©2011 University of Illinois Board of Trustees

The balanced chemical equation provides information about the beginning and end of reaction. The reaction mechanism gives the path of the reaction. Mechanisms.

Collision Theory & Reaction Mechanisms

Chpt 12 - Chemical Kinetics Reaction Rates Rate Laws Reaction Mechanisms Collision Theory Catalysis HW set1: Chpt 12 - pg , # 22, 23, 28 Due Jan.

Given the rxn: 2NO (g) + O 2(g) -> 2NO 2(g) Express the reaction rate in terms of O 2 and NO 2. If O2 is reacting at a rate of M/s, at what rate.

Reaction Mechanisms A balanced equation tells us the reactants and products, but does not tell us how the reactants became products. Vocabulary: 1.Reaction.

Reaction Mechanism Chapter 14 part V

Chemical Kinetics Chapter 15 H 2 O 2 decomposition in an insect H 2 O 2 decomposition catalyzed by MnO 2.

Rates of Chemical Reactions CHEMICAL KINETICS. The rate of a reaction is measured by looking at the change in concentration over time. RATES OF CHEMICAL.

Chemical Kinetics. Kinetics The study of reaction rates. Spontaneous reactions are reactions that will happen - but we can’t tell how fast. (Spontaneity.

Chapter 13 Chemical Kinetics CHEMISTRY. Kinetics is the study of how fast chemical reactions occur. There are 4 important factors which affect rates of.

Rate Mechanisms The Basics. Reaction Mechanisms O The series of steps that actually occur in a chemical reaction. O Kinetics can tell us something about.

Reaction Mechanism. l Process by which a reaction occurs l Reaction occurring in a single event or step its called an elementary reaction l Total reaction.

CHAPTER 14: KINETICS Dr. Aimée Tomlinson Chem 1212.

Rate Expression and reaction mechanism

Chapter 14: Kinetics Dr. Aimée Tomlinson Chem 1212.

CHE1031 Lecture 10: Reaction kinetics

Reaction Mechanisms -Catalysis

Integrated rate laws 1st order ln[A] = -kt + ln[A]0 rate = k[A]

Integrated rate laws ln[A] = -kt + ln[A]0 rate = k[A]

Chapter 14: Chemical Kinetics

Reaction Mechanisms.

Brown, LeMay, Ch 14 AP Chemistry

Reaction Mechanisms Glenn V. Lo, Ph.D. Department of Physical Sciences

Reaction Mechanism.

Reaction Mechanisms Chemical Kinetics-5.

Reaction Mechanisms A reaction mechanism is a sequence of molecular events, or reaction steps, that defines the pathway from reactants to products.

WARM UP The rate constant for the 2nd order reaction

Reaction Mechanisms -- the processes by which reactions occur --

Integrated rate laws ln[A] = -kt + ln[A]0 rate = k[A]

Part 3: Reaction Mechanisms

Reaction Mechanisms.

Reaction Mechanisms Elementary Steps Phenomenon Examples Rate Law

Reaction Mechanisms.

Rate Law and Mechanics A + 2B C 2 B E (slow) E + A C (fast)

Factors that Affect Reaction Rate Constant

Reaction mechanism Most reactions occur in a series of steps. Most you don’t see. The reaction mechanism is these series of steps.

Reaction Mechanisms Most chemical reactions occur by a series of steps called the reaction mechanism. The overall progress of a chemical reaction can be.

Reaction Pathways.

Announcements Welcome back!

Kinetics Chapter 14.

Integrated rate laws zero order t1/2 = [A]0 2k rate = k.

Chemical Kinetics Lesson 2

Reaction Mechanisms Most reactions occur in a series of steps

12.6 Reaction Mechanisms Discuss #11

Reaction Mechanisms.

Reaction Mechanism Chapter 14 part V

Integrated rate laws 1st order ln[A] = -kt + ln[A]0 rate = k[A]

Presentation transcript:

1 Reaction Mechanisms: Reaction is broken into steps with intermediates being formed. “some RXNS occur in one step, but most occur in in multiple steps.” Each Step is called an elementary step, and the number of molecules involved in each step defines the molecularity of the step. unimolecular: = 1 i.e. O 3 *  O 2 + O bimolecular: = 2 (these are the most common) i.e. HI + HI  activated complex  H 2 + I 2 termolecular: = 3 (rare, due to probability of orientation and energy both being correct.) i.e. O(g) + O 2 (g) + N 2 (g)  O 3 (g) + “energetic” N 2 (g)

2 The Raschig process for the preparation of hydrazine (N 2 H 4 ) Overall RXN: 2NH 3 (g) + NaOCl(aq)  N 2 H 4 (aq) + NaCl(aq) + H 2 O(l) Proposed Mechanism: (Only from experiment) Step 1: NH 3 (aq) + OCl - (aq)  NH 2 Cl(aq) + OH - (aq) Step 2: NH 2 Cl (aq) + NH 3 (aq)  N 2 H Cl - (aq) Step 3: N 2 H 5 + (aq) + OH - (aq)  N 2 H 4 (aq) + H 2 O(l) “Cancel intermediates and “add steps” to give overall RXN.” 2NH 3 (g) + OCl - (aq)  N 2 H 4 (aq) + Cl - (aq) + H 2 O(l) The overall rate law, mechanism, and the total order can’t be predicted from the stoichiometry, only by experiment.

3 The following is only true for individual steps: The rate law of an elementary step is given by the product of a rate constant and the conc. of the reactants in the step. Step Molecularityrate law A  Product(s) uni rate = k[A] A + B  Product(s) bi rate = k[A][B] A + A  Product(s) bi rate = k[A] 2 2A + B  Product(s) ter rate = k[A] 2 [B] The overall mechanism must match the observed rate law. Usually one STEP is assumed to be the rate determining step.

4 Example: Overall RXN: 2NO 2 (g) + F 2 (g)  2NO 2 F(g) Observed Experimental rate law: rate = k[NO 2 ][F 2 ] Question:Why does this rule out a single step RXN? Answer: rate law for single step process would be: rate = k[NO 2 ] 2 [F 2 ] “Let’s try to work out a Mechanism that matches the observed rate law.”