Introduction

Imagine a bus driving along a city road.  Along the bus route, some passengers board the bus, and some passengers disembark from the bus.  If there is the same number of people boarding and disembarking, then the number of passengers riding the bus does not change, even though the identities of the passengers may vary.  This is an example of a dynamic phenomenon called equilibrium.  We expand on what we learned in Unit 2 about reaction rates.  Chemical systems achieve equilibrium when the forward and reverse reaction rates are equal.  The chemical reaction continues to proceed, but there is no net change in the quantity of reactants or products.

Unit 3 Sections

3.1 Microscopic and Macroscopic Aspects of Equilibrium

3.2 Le Châtelier’s Principle

3.3 The Equilibrium Quotient and Constant

3.4 Equilibrium Calculations

Each section has a reading portion, self-check question, and a set of practice exercises with solutions.  This course has a strong emphasis on solving problems by applying concepts from the reading portions.  Thus, working through the self-check questions and practice exercises is important for learning how to apply concepts in chemistry. The supplementary resources and supplementary activities within the sections are not for marks but provide alternative perspectives to enhance understanding of the course material.