Chemical Equilibrium -- What Are the Characteristics of Equilibrium Reactions?

Cheryl Coolidge, Colby-Sawyer College, New London NH
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This material is replicated on a number of sites as part of the SERC Pedagogic Service Project


In this Spreadsheets Across the Curriculum activity, students create spreadsheets to examine the time course of a reaction that goes to completion and compare it to the time course of a reaction that reaches equilibrium. Students input both the rates of the forward and the reverse reactions into the spreadsheets and study the relationship between relative reaction rates and the extent of reaction completion.

Learning Goals

Students will:
  • Create two spreadsheets that demonstrate the time course of a reaction that goes to equilibrium vs. a reaction that goes to completion. The equations needed to complete these spreadsheets involve calculations of rate of change and percent change.
  • Create graphs of time vs. percent change using an XY scatter plot.
  • Make predictions about the effects of changing the starting number of molecules, the forward and the reverse rates, and the ratio of the forward to the reverse rate.
In the process the students will:
  • Continue to learn to use Excel to do calculations easily.
  • Distinguish between rate of change and percent change,
  • Use graphs to visualize the difference between an equilibrium reaction and a reaction that goes to completion.
  • Model the effect of controlling variables on a chemical reaction.

Context for Use

This module is intended for use in an introductory chemistry course for science majors, typically during the second semester of a year-long course. It is also appropriate for an AP chemistry course.

Description and Teaching Materials

SSAC2005.QD450.GCC1.1-student (PowerPoint 388kB May27 10)

The module is a PowerPoint presentation with embedded spreadsheets. If the embedded spreadsheets are not visible, save the PowerPoint file to disk and open it from there.

This PowerPoint file is the student version of the module. An instructor version is available by request. The instructor version includes the completed spreadsheet. Send your request to Len Vacher ( by filling out and submitting the Instructor Module Request Form.

Teaching Notes and Tips

The module is constructed to be a stand-alone resource. It can be used as a homework assignment or lab activity. It can also be used as the basis of an interactive classroom activity.


The last two slides are an end-of-module assignment that can be used for assessment.

References and Resources