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Ch.13 - Chemical KineticsWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Sections
Intro to Chemical Kinetics
Energy Diagrams
Catalyst
Factors Influencing Rates
Average Rate of Reaction
Stoichiometric Rate Calculations
Instantaneous Rate
Collision Theory
Arrhenius Equation
Rate Law
Reaction Mechanism
Integrated Rate Law
Half-Life

A Reaction Mechanism is a step-by-step sequence of elementary steps by which an overall chemical change occurs.

Understanding Reaction Mechanism

Concept #1: Reaction Mechanism Overview

Example #1: Consider the following reaction mechanism for the formation of nitrobenzene:

HNO3 (aq) + H2SO4 (aq)  → H2NO3+ (aq) + HSO4 (aq)                   

H2NO3+ (aq) + C6H6 (aq) → C6H6NO2+ (aq) + H2O (l)           

C6H6NO2+ (aq) + HSO4 (aq) → H2SO4 (aq) + C6H5NO2 (aq)                                   

Identify the reaction intermediate(s) and catalyst(s).

Concept #2: Molecularity

Example #2: The elementary reaction, 2 NO2 (g) + F2 (g)2 NO2F (g) , is an example of a _____________ reaction.

Concept #3: Rate Law Determination

Example #3: Consider the following elementary steps. What is the rate law of the reaction mechanism?

 N2O5 (g) ⇌ NO(g) + NO(g)                                       [Fast]

 NO(g) + N2O5 (g) → 3 NO2 (g) + O(g)                   [Slow]

 NO3 (g) + O (g) → NO (g) + O3 (g)                             [Fast]

Practice: Consider the following elementary steps:

NO2 (g) + NO2 (g) → NO4 (g) + NO (g)           [SLOW]
NO (g) + CO3 (g) → N (g) + CO4 (g)                 [FAST]

What is the rate law of the reaction mechanism?

Practice: The following reaction of 2 Br2 (g) + 2 NO (g) → N2 (g) + 2 Br2O (g) has the following rate law: Rate = k [Br2][NO]2. The proposed mechanism for the reaction is:

Br2 (g) + NO2 (g) → N (g) + Br2O (g)            [SLOW]
N (g)  +  NO (g) → N2 (g) + O (g)                  [FAST]
O (g)  +  Br2 (g) → Br2O (g)                          [FAST]

Which of the following statements is/are false?

a) The rate determining step is bimolecular.
b) There are three elementary steps in the reaction mechanism.
c) The mechanism possesses a catalyst.
d) O is the only reaction intermediate in this reaction mechanism.
e) This is not a valid mechanism for the reaction.