Chemistry - A Molecular Science

Chapter 9 Reaction Energetics

9.0 Introduction

9.7 Free Energy and Reaction Spontaneity

9.1 The First Law of Thermodynamics

9.8 Standard Free Energy and the Extent of Reaction

9.2 Enthalpy

9.9 Activation Energy

9.3 Enthalpies of Combustion

9.10 Rates of Reaction and the Rate Law

9.4 Bond Energies

9.11 Equilibrium and the Equilibrium Constant

9.5

Entropy 9.12

LeChâtelier’s

Principle

9.6

The Second Law of Thermodynamics

9.13 Chapter Summary and Objectives

9.14 Exercises

9.0

INTRODUCTION

The energy released in chemical reactions play

s an important role in our lives as it is used

to heat our homes, run our cars, power

our factories, and even keep our bodies

functioning. We now expand our understanding of the flow of

energy and its utilization in

a study of

thermodynamics

, the study of energy and its transformations, and

thermochemistry

, the branch of thermodynamics that focuses on the energy involved in

chemical reactions. Thermodynamics is concerned only with energy differences between the initial and final states of a process, not with how the initial state is converted into the final state. Similarly, thermochemistry d

eals with the energy difference between the

reactants and products, not with how the r

eaction takes place. The process by which the

reactants are transformed into the products is the domain of

chemical kinetics

, the study

of the rates and mechanisms of chemical r

eactions. In this chapter, thermodynamics and

kinetics are combined under the broader term

reaction energetics

in our study of why and

how reactions occur. THE OBJECTIVES OF CHAPTER 9 ARE TO: •

explain the principles of the first and second laws of thermodynamics;

-^

define the enthalpy of reaction

and relate it to bond energies;

• define entropy; •^

explain how the order of a system c

an be used as a predictor for its entropy;

-^

describe the thermodynamic driving force behind a reaction;

-^

describe the energy changes requir

ed to convert reactants to products;

-^

discuss the rate law of a reaction;

-^

write rate laws for elementary processes;

-^

describe the equilibrium process and define the equilibrium constant; and

-^

describe Le Châtelier’s principle and ap

ply it to systems at equilibrium.

Chapter 9 Reaction Energetics

© by

North

Carolina

State

University