Module 7

Module 7—Principles of Chemical Equilibrium

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The Haber process to make ammonia provides an important example of the importance of forward and reverse reactions in a chemical system. Read “The Haber Process” on page 325 in the textbook.

 

The problems encountered when trying to increase the yield of ammonia are evidence that a reverse reaction is an important aspect of this system. It can occur at the same instant as the forward reaction and in the same reaction vessel.

 

     N2(g) + 3 H2(g) 2 NH3(g)

 

In designing a system to maximize the yield of ammonia, experimentation with pressures, temperatures, and catalysts is intended to favour the forward reaction so that large quantities of product can be made. During unsuccessful trials, large quantities were not achieved. In Lesson 6 you will learn more about conditions that may favour the forward or reverse reaction. For now, it is important to understand that both processes exist within a system.

 

In Lesson 1 you learned that a system at equilibrium is a closed system that has constant properties or does not appear to change. In this lesson you have learned that an equilibrium also involves a forward and a reverse reaction. How do all of these ideas connect? Use the following activity to demonstrate your understanding of these aspects of an equilibrium.

 

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Use the following statement to answer questions TR 1–3: A system at equilibrium is a closed system that has constant properties.

 

TR 1. Interpret the statement by describing the rate of reaction of the forward and reverse processes for a system that is at equilibrium.

 

TR 2. Interpret the statement by describing the rates of the forward and reverse reaction for a system that is approaching equilibrium.

 

TR 3. Provide one observation to support your answer to TR 2.

 

Save your work in your course folder and submit a copy to your teacher.

 

Read

 

Read page 677 in the textbook to learn more about the different types of equilibria that can exist in chemical systems.

 

Self-Check

 

SC 1. Provide an example of each type of chemical equilibrium described on page 677 of the textbook. Identify the chemical components involved.

 

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