Introduction to Equilibrium

1. Introduction

The Equilibrium Unit is dedicated to a study of chemical equilibrium. In the first part, Systems in Equilibrium, you will investigate the principles of chemical equilibrium. In the second part, Acids and Bases, you will expand upon these principles as you investigate the equilibrium of acid-base systems.

Throughout the Equilibrium Unit you will rely on your skills as an observer, and you will develop skills to predict changes that may occur to equilibrium systems. As you have done in other units in this course, you will also rely on your knowledge of diagnostic tests to check your predictions and to confirm you understanding of principles affecting chemical equilibrium.   You will learn to describe and analyze equilibrium systems from a range of perspectives. In addition to qualitative descriptions, you will describe equilibrium systems from a quantitative perspective.

In Systems of Equilibrium, you will use ICE tables and the equilibrium constant, K_eq, to describe an equilibrium from a quantitative perspective. You will further apply this understanding in Acids and Bases by using the equilibrium constants for acids and bases, K_a and K_b.

At the end of Equilibrium Unit you will be able to

• explain that there is a balance of opposing reactions in chemical equilibrium systems
• determine quantitative relationships in simple equilibrium systems

2. Bigger Picture

In the Module Introduction you read that there are examples of equilibrium all around you. You are probably questioning whether this is true. Soil is often overlooked when we think of important parts of Earth. In earlier science courses you learned that soil is a component of the biosphere, the section of Earth that supports life. Apart from being the medium for growing most plants, soil is the home for many organisms. Soil is also made up of many chemical components. The minerals, organic materials, and water within soil form a complex chemical system.

The atmosphere also forms a system in which equilibria can exist. How might these equilibria affect the rain and other forms of precipitation that will deposit on Earth?   In this module you will be introduced to a number of chemical systems in which equilibrium is critical to each system’s function. You will also learn that equilibrium systems exhibit certain unique properties that can be manipulated by the application of a stress. Studying equilibrium is not only a matter of knowing the system; studying equilibrium also involves knowing the changes that can occur within the system that help to describe the equilibrium. In your study you will learn about forward and reverse reactions, conditions, and stresses; all of which define a chemical equilibrium. You will do more than study the basic principles of a system at equilibrium; you will learn how manipulating conditions can allow you to understand a chemical equilibrium. What kinds of stresses are placed on soil? Does human activity or agricultural practice affect the equilibrium of chemical components in soil? How would the chemical components in soil respond to the application of a stress, and what impact might that stress have on soil’s fertility? Soil is not the only system that has chemical components that form an equilibrium system. In this module you will also investigate the components within biological systems that make up equilibrium systems within organisms.

3. System in Equilibrium

In Systems of Equilibrium you will examine chemical equilibrium. Chemical equilibrium is something you may not have thought much about, but it is present and it affects many of the chemical systems you have investigated in this course. For example, in the last module you prepared esters. When you cooled the esters on ice, you were manipulating an equilibrium so that you would be better able to collect and observe the ester you had synthesized.

Other examples of chemical equilibrium are found in biological systems, chemical interactions, and industrial applications. In this module you will investigate many systems and how they demonstrate the principles of systems at equilibrium. You will learn how equilibrium can be classified, studied, and manipulated. You will learn how to predict changes to equilibrium when a system that appears to remain constant is stressed, and you will learn the scientific principles involved when systems are stressed.

In System in Equilibrium you will investigate the following questions:

• What is happening in a system at equilibrium?
• How do scientists predict shifts in the equilibrium of a system?

As you approach the end of the module, you will come to understand many aspects of equilibrium and how systems in equilibrium behave. You will be asked to pay special attention to specific properties of each of the systems you investigate.

4. Acids and Bases

In the Acids and Bases Unit you will apply your understanding of the principles of equilibrium to chemical systems containing aqueous acids and bases. You will use your knowledge of dynamic equilibrium, equilibrium position, and shifts in equilibrium. You will also rely on your ability to analyze an equilibrium system using quantitative techniques (like calculating a value for the equilibrium constant, K_eq) and your ability to complete an ICE table.

Your study of the equilibrium of aqueous acids and bases will include an investigation of environmental and biological systems. You will investigate how the components of these systems can interact to form equilibrium systems, and you will consider how the behaviour of these systems can be better understood through knowledge of the principles of chemical equilibrium.

In the Acids and Bases Unit you will investigate the following question:

• How does the equilibrium of acids and bases affect environmental and biological systems?

5. Check Your Understanding

Click here to attempt the PreQuiz for this unit.  You must earn at least a 70% on the PreQuiz before you are able to proceed to the first lesson.

6. Continue to First Lesson

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