reaction kinetics chapter 17 modern chemistry
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Reaction Kinetics Chapter 17 Modern Chemistry. Sections 1 & 2 The Reaction Process Reaction Rate. Section 17.1. The Reaction Process. Reaction Mechanisms. H 2 (g) + I 2 (g) 2HI (g). This balanced equations doesn’t show the steps of this reaction. - PowerPoint PPT PresentationTRANSCRIPT
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Reaction Reaction KineticsKinetics
Chapter 17 Chapter 17 Modern Modern
ChemistryChemistry
Sections 1 & 2Sections 1 & 2The Reaction The Reaction
ProcessProcessReaction RateReaction Rate
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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The The Reaction Reaction ProcessProcess
Section 17.1Section 17.1
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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This balanced equations doesn’t show This balanced equations doesn’t show the steps of this reaction.the steps of this reaction.
TheThe step-by-step sequence of reactions by which the overall chemical change occurs is a Reaction Mechanism.
Reaction MechanismsReaction Mechanisms
H2 (g) + I2 (g) 2HI (g) H2 (g) + I2 (g) 2HI (g)
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Only the net chemical change is directly observable for most chemical reactions.
Even a reaction that appears from its balanced equation to be a simple process may actually be the result of several simple steps
Reaction MechanismsReaction Mechanisms
H2 (g) + I2 (g) 2HI (g) H2 (g) + I2 (g) 2HI (g)
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Step 1: I2 ↔ 2I
Step 2: 2I + H2 ↔ 2HI
I2 + H2 ↔ 2HI
2I is not in the final equation
Reaction MechanismsReaction Mechanisms
H2 (g) + I2 (g) 2HI (g) H2 (g) + I2 (g) 2HI (g)
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Step 1: I2 ↔ 2I
Step 2: 2I + H2 ↔ 2HI
I2 + H2 ↔ 2HISpecies that appear in some steps
but not in the net equation are known as intermediates.
Reaction MechanismsReaction Mechanisms
H2 (g) + I2 (g) 2HI (g) H2 (g) + I2 (g) 2HI (g)
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Step 1: I2 2I
Step 2: I + H2 ↔H2I
Step 3: H2I + I ↔2HI
I2 + H2 ↔2HI
Homogeneous reaction, a reaction whose reactants and products exist in a single phase.
Reaction MechanismsReaction Mechanisms
H2 (g) + I2 (g) 2HI (g) H2 (g) + I2 (g) 2HI (g)
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Step 1: I2 2I
Step 2: I + H2 ↔H2I
Step 3: H2I + I ↔2HI
I2 + H2 ↔2HI
Reaction MechanismsReaction Mechanisms
H2 (g) + I2 (g) 2HI (g) H2 (g) + I2 (g) 2HI (g)
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Reacti
on
Mech
an
ism
Reacti
on
Mech
an
ism
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Rate
Dete
rmin
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Ste
pR
ate
Dete
rmin
ing
Ste
p
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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In order for reactions to occur between substances, their particles must collide.
The particles must collide with the CORRECT ORIENTATION and with SUFFICIENT ENERGY to break the bonds.
Collision TheoryCollision Theory
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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3 Possible Collisions3 Possible Collisions
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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HI CollisionsHI Collisions
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Acti
vati
on
En
erg
yA
cti
vati
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En
erg
y
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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The bonds of these reactants must be broken in order for new bonds to be formed.
Bond BREAKING is an ENDOTHERMIC process, and bond FORMING is EXOTHERMIC.
Activation energy, Ea, is the minimum energy required to transform the reactants into an activated complex.
Activation EnergyActivation Energy
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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An activated complex is a transitional structure that results from an effective collision and that persists while old bonds are breaking and new bonds are forming .
An activated complex occurs at a high energy position along the reaction pathway.
An activated complex is not the same as an intermediate. – An activated complex is short-lived
Activated ComplexActivated Complex
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Ch 17 Sec 1 HomeworkCh 17 Sec 1 Homework
Page 567 # 1-8
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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En
erg
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rofi
leEn
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rofi
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p. 564p. 564
Ea
E
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Ea = energy of activated complex − energy of reactants [reactants to A.C. on graph]
Ea′ = energy of activated complex − energy of products [products to A.C. on graph]
ΔEforward = energy of products − energy of reactants [reactants to products on graph]
ΔEreverse = energy of reactants − energy of products [products to reactants on graph] |Eforward | = |Ereverse |
same value; opposite sign
Energy ProfilesEnergy Profiles
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Endothermic Energy ProfileEndothermic Energy Profile
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Exothermic Energy ProfileExothermic Energy Profile
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p. 565p. 565
En
erg
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rofi
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or
En
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rofi
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or
HI
Syn
thesis
HI
Syn
thesis
notes
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Copy the energy diagram below, and label the reactants, products, E, Ea, and Ea′. Determine the value of Eforward , Ereverse , Ea, and Ea′.
Sample Problems p. 566Sample Problems p. 566
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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ΔEforward = energy of products − energy of reactants
ΔEforward = 50 kJ/mol − 0 kJ/mol = +50 kJ/mol
ΔEreverse = energy of reactants − energy of products
ΔEreverse = 0 kJ/mol − 50 kJ/mol = − 50 kJ/mol
Sample Problems p. 566Sample Problems p. 566
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Ea = energy of activated complex − energy of reactants
Ea = 80 kJ/mol − 0 kJ/mol = 80 kJ/molEa′ = energy of activated complex − energy of productsEa′ = 80 kJ/mol − 50 kJ/mol = 30 kJ/mol
Sample Problems p. 566Sample Problems p. 566
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1. a. Use the method shown in the sample problem to redraw and label the following energy diagram. Determine the value of ΔEforward, ΔEreverse, Ea, and Ea′.
b. Is the forward reaction shown in the diagram exothermic or endothermic? Explain your answer.
Practic Problems p. 567Practic Problems p. 567
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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2. a. Draw and label an energy diagram similar to the one shown in the sample problem for a reaction in which Ea = 125 kJ/mol and Ea′ = 86 kJ/mol. Place the reactants at energy level zero.
b. Calculate the values of ΔEforward and ΔEreverse.
c. Is this reaction endothermic or exothermic? Explain your answer.
Practic Problems p. 567Practic Problems p. 567
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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3. a. Draw and label an energy diagram for a reaction in which Ea = 154 kJ/mol and ΔE = 136 kJ/mol.
b. Calculate the activation energy, Ea′, for the reverse reaction.
Practic Problems p. 567Practic Problems p. 567
Chapter 17 Section 1 The Reaction ProcesChapter 17 Section 1 The Reaction Process p. 560-567s p. 560-567
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Ch 17 Sec 1 HomeworkCh 17 Sec 1 Homework
Energy Diagram Worksheet