Unit 3. Reaction Equilibrium

This website provides learning and teaching tools for a first course on kinetics and reaction engineering. The course is divided into four parts (I through IV). Here, in Part I of the course, a brief review of some basic concepts related to chemical reactions is presented. Students taking their first kinetics and reaction engineering course should already be familiar with most of the material that is presented in this part of the course. The concepts that are reviewed here will be utilized repeatedly throughout the remainder of the course, and therefore it is critically important to master them before proceeding to the main body of the course, Parts II, III and IV.

Unit 3 examines the calculation of equilibrium “constants” at 298 K and at arbitrary temperatures and the use of those constants for the calculation of the equilibrium composition of a reacting mixture. Doing so requires application of the concepts presented in Units 1 and 2. Reaction equilibrium is relevant to kinetics and reaction engineering in a few ways. First, the equilibrium constant often appears in rate expressions for reversible reactions, and so one needs to know how to calculate it. In addition, one of the first steps to take in a reaction engineering analysis is to determine the equilibrium limitations, if any, on the reactions in the system of interest. This unit completes Part I of this course.

Learning Resources

• Archive (.zip) - Contains all learning resources listed below for this unit, except for the simulators
• Documents to Read:
  • Unit 03 Informational Reading (.pdf)
  • Example 3.1 (.pdf)
  • Example 3.2 (.pdf)
• Videos to Watch (please right-click and save, then play back locally on your computer):
  • Unit 03 Informational Video (.mov)
  • Example 3.1 Video (.mov)
  • Example 3.2 Video (.mov)
• Reference Files:
  • Unit 3 Definitions, Nomenclature and Equations (.pdf)
  • How To Calculate an Equilibrium Constant (.pdf)
  • How To Calculate the Equilibrium Composition of a Reacting Mixture (.pdf)
• Other Files:
  • Example_3_1.m - MATLAB file used in the solution of Example 3.1
  • Example_3_2.m - MATLAB file used in the solution of Example 3.2
  • Reaction Thermodynamics Simulators
    • Methyl Chloride Synthesis (zipped .jar file)
    • Reverse Water-Gas Shift (zipped .jar file)
    • Methanol Synthesis (zipped .jar file)
     
    Please note that these simulators are intended for educational purposes only. They should not be used for any other purpose, and if they are, the author does not bear any responsibility or liability for the consequences.
     
    The “zipped .jar file,” when unzipped, will produce a folder that contains a .jar file and a folder named "lib". Not surprisingly the latter folder contains additional libraries and files that the simulator uses. To run the simulator, launch the .jar file either from the command line using java -jar [name of .jar file], or by double clicking it if your operating system supports it. The simulators require JAVA 1.6 or later in order to run. There is a User's Guide under the Help menu that describes how to use the simulators.
     
    

Teaching Resources

• Archive (.zip) - Contains all teaching resources listed below for this unit, except for the simulators
• Sample Class
  • Online Pre-class Quiz (.pdf file)
  • Redacted slides to make available to students before class
    • Keynote 09
    • PowerPoint
  • Class Lesson Plan (.pdf)
  • Learning Activity Files to make available to students before class
    • Activity 1 Worksheet (.pdf) - to the in-class activity problems
  • Complete slides to make available to students after class
    • Keynote 09
    • PowerPoint
• Alternative Questions (.pdf) that could be used in a pre-class quiz
• Alternative In-Class Learning Activities
  • Alternative Activity 3.1 (.zip) - an activity where students will calculate the equilibrium composition when a single reaction that forms a solid product occurs.
  • Alternative Activity 3.2 (.zip) - an activity where students use thermodynamic equilibrium simulators to observe trends in the equilibrium constants and compositions.
• Simulator Source files
  • Methyl Chloride Synthesis (zipped Netbeans project folder)
  • Reverse Water-Gas Shift (zipped Netbeans project folder)
  • Methanol Synthesis (zipped Netbeans project folder)
   
  Please note that these simulators are intended for educational purposes only. They should not be used for any other purpose, and if they are, the author does not bear any responsibility or liability for the consequences.
   
  The “Netbeans Project folders” contain the Netbeans java project used to create them. Providing them in this way will allow instructors or students familiar with java and the Netbeans development environment to modify them. They were developed using version 6.7 of Netbeans. They use the Swing Application Framework, which is not supported in version 7.1 or higher of the Netbeans IDE. They are no longer in development, and I am not available to consult on any issues encountered when using them.

Practice Problems

1. Formic acid can decompose two ways as given in equations (1a) and (1b). If pure formic acid decomposes at 200 °C and 1 atm, what is the final equilibrium composition in mole percentages? In solving this problem, assume that all species behave as ideal gases. You will need to consult an appropriate reference source to find the necessary thermodynamic data.

(Problem Statement as .pdf file)

2. The water-gas shift reaction was described in practice problem 2.1. That reaction can also take place in the reverse direction, that is as shown in equation (2a). When this happens, the reaction is sometimes referred to as the reverse water gas shift. Calculate the equilibrium mole fraction of CO for a process that starts with equal amounts of carbon dioxide and hydrogen and that takes place at 2 atm and 190 °C. You will need to consult an appropriate reference source to find the necessary thermodynamic data.

(Problem Statement as .pdf file)

3. If air (78% N₂, 22% O₂) reacts at 600 °C and atmospheric pressure and reactions (3a) through (3c) reach equilibrium, what will the mole percentages of N₂O, NO and NO₂ equal? Heat capacity (cal mol^-1 K^-1) expressions for the reagents are given in equations (3d) through (3h); the standard heats of formation at 298 K of N₂O, NO and NO₂ are 19.49, 21.6 and 8.09 kcal mol^-1, respectively; their standard Gibbs free energies of formation at 298 K are 24.77, 20.72 and 12.42 kcal mol^-1, respectively. (Problem Statement as .pdf file)