Chapter 15 Chemical Kinetics

Rates of Chemical Reactions

The Effect of Temperature on Reaction

Other Factors Affecting the Rates of reactions

Rate Expression Slope of the tangent line Initial Rate

Exercise 1 Time(min)[CH 3 COOPh] (mol/L)

Time(min)[CH 3 COOPh] (mol/L) Exercise 1

Exercise 2 2 NO(g) + 2 H 2 (g)  N 2 (g) + 2 H 2 O(g) Reactant Concentration (mol/L)Rate of Appearance of N 2 (mol/L·s) [NO][H 2 ] Run 1: Run 2: Run 3: Run 4:

Use in graphical methods Plot for shape of rate response Integrated Rate Expressions

Zero Order Rate Expression

First Order Rate Expression Conc Vs Time

Half Life

Second Order Rate Expression Conc VS Time

Effect of Temperature on the Rate Constant Increasing Concentration

The Reaction Coordinate A + B AB A B d AB A B A B

Temperature and Activation Energy

Arrhenius Pre-exponential Factor

Exercise 3 Temp( o C)K(1/Ms) * * * * *10 -2

Exercise 3 T( o C)T(K)k1/Tln k E E E E E

Effect of Catalyst on the Rate Constant

Catalytic Hydrogenation CH 2 =CH 2 + H 2 CH 3 -CH 3

Elementary StepMolecularityRate Equation A  prod. UnimolecularRate = k[A] A + B  prod. BimolecularRate = k[A]·[B] A + A  prod. BimolecularRate = k[A] 2 2 A + B  prod. TermolecularRate = k[A] 2 ·[B] Reaction Mechanisms

The Bimolecular Substitution Reaction [Br····CH 3 ····Cl] - BrCH 3

The Unimolecular Substitution Reaction Br - + [CH 3 ] + BrCH 3 + BLOCK [CH 3 ] +

This reaction has two transition states The Unimolecular Mechanism Requires an Intermediate

Exercise 4

Time (min)[PhAc] (mol/L)ln[PhAc]1/[PhAc]

Slope=-k = min -1 Exercise 4

Concepts from Chapter 15 Rate constants Rate laws Integrated rate equations Zero-order, first-order and second-order reactions Half life, t 1/2 Collision theory Activation energy and the Arrhenius equation(s) Catalysts Reaction co-ordinates, intermediates and transition states Reaction mechanisms and elementary steps Molecularity - rate equations for elementary steps Rate determining steps Supporting/disproving a proposed mechanism using kinetic data