Equilibrium  &  LeChatelier's Principle
                              Ms. Leslie Bailey
Introduction Standards Objectives Activities Assessment Results Resources 
                                                                                                
Introduction
        This lesson is a qualitative look at  Chemical  Equilibrium.  As an introduction to LeChatelier's Principle, students will first need to understand what equilibirium is and how equilibrium can be recognized.  My lesson will conclude with students using  LeChatelier's  Principle  to predict  how a system at equilibrium will respond to imposed changes. 
Subject :     Chemistry
Topic:      Chemical Equilibrium
Grade Level:      10 - 12
Student Lesson name and URL: 
    http://ctap295.ctaponline.org/~baileyl/student/index.html
California State Standards Addressed : 

1. Students will be able to define chemical equilibrium as a dynamic process at the molecular level, established when forward and reverse reaction rates are equal. 

2.  As a basis for understanding this concept (#1), students will know how to use LeChatelier's Principle to predict the effect of changes in concentration, temperature and pressure. 

3.  * Students will know how to write and calculate an equilibrium constant expression for a reaction.
 
 
 
 
 

Instructional  Objectives:

  • After viewing several demonstrations, a power point presentation,  reading assigned pages, and viewing a video, students will be able to:  ( 1 ) define chemical equilibrium,  ( 2 ) recognize when equilibrium is established,  and  ( 3 ) compare what is happening on the microscopic and macroscopic levels during equilibrium. 
  • After completing an experiment and viewing the graphical depiction of concentration & reaction rate changes over time on a chemistry CD, students will be able to: ( 1 )  identify the relative concentration of reactants and products at equilibrium, and ( 2 ) identify the relative reaction rates for the forward and reverse reactions  at  equilibrium. 
  • After collecting information through an online assignment, observing several demonstrations, completing an in-class chemical experiment, and completing  a virtual experiment online, students will be able to:  ( 1 ) identity which factors affect equilibirum,   ( 2 )  define LeChatelier's Principle,   and ( 3 ) use LeChatelier's Principle to describe the effect of changing the temperature, concentration, pressure, and volume of a system at equilibrium,     ( 4 ) determine whether a system at equilibrium is endothermic or exothermic,   ( 5 ) write the equilibirum law expression for a reaction, and  ( 6 ) complete calculations based on  Keq.
Student Activities

  Day 1 ( Special block schedule today - 2 hour classes ) 

      A. Introductory Activity: 

              1.  At the beginning of this unit, you will complete an Equilibrium pre-test.   You will then
     be tested on the same material at the end of  the unit , so that I can evaluate both  your
     completion of the objectives and my use of integrating technology into my lessons. 

  B. Enabling Activities:

               2.  After observing and discussing the following demonstrations, you will be able to
     complete objective 1:   Students will be able to  define chemical equilibrium, 

                      a) acetone & manometer demo:  acetone vapor & liquid phases attaining equilibrium
                           within closed manometer, 
                      b) KMnO4 & water demo :  solid & aqueous solubility equilibrium attained within beaker, 
                      c)  NO2  = N2O4 gas tubes demo :  chemical equilibrium established within sealed tubes. 

               3.  After observing and discussing  the ChemStudy movie "Equilibrium" ,   you will
     review objective 1 & be introduced to objective 2:  Students will be able to compare what is
  happening on the microscopic and macroscopic levels during equilibrium. 
 

  C. Culminating & Assessing Activity :

  Homework:

                 4.  Review today's objectives by visiting  the following link: 
            http://www.capital.net/com/vcl/equil/equil.htm

   Once you visit this link, follow these steps: 
      a. You will start at the Introduction page of  Virtual Chemistry Lab - Equilibrium & LeChatelier's 
Principle. Read it , then, 
      b. click on the background button, read that page, then, 
      c.  click on continue with more background on equilibrium link for more information  read that page, 
then STOP (or go back to Introduction page).   You are done with the online reading for now! 

 Now,  after  visiting:  http://www.capital.net/com/vcl/equil/equil.htm , write or print out your answers to
the following questions: 

       When a chemical system is in equilibrium a number of items are true: 

      1.  The rates of the forward and reverse reactions are_________. 
      2.  The concentrations of all the substances involved _________. 
      3.  This happens because the products and reactants are being formed __________. 
      4.  There will be both ____________present but the concentrations of them will not necessarily be equal. 
      5.  A system at equilibrium is said to be a dynamic one.  Why? 

  PLEASE  NOTE :  ( I wanted this first online assignment to be easy, and it is, I really just wanted to 
see how many of you were successful at  getting online and following the lesson.) 
Come in ready to go tomorrow! 
 
 

  Day 2 ( Special block schedule today - 2 hour classes ) 
 

  A. Introductory Activity:

              1. After reviewing and discussing the homework, and observing a Powerpoint presentation on Equilibrium,
you will review objectives 1 & 2.   The Powerpoint presentation will review the following ideas: 

       a.  What is equilibrium? 
       b.  How is equilibrium recognized?, 
       c.  What conditions must exist in order for equilibrium to be attained? and, 
       d.  Why is chemical equilibrium said to be dynamic? 

My powerpoint presentation will also introduce the question : 

        e. At equilbrium, must the concentration of reactants and products at be equal? 

       B. Enabling Activity:

               2.  You will complete a lab ( page 1 of lab activities, Unit 10 )  called:   Establishing Equilibrium
    This is an activity which will simulate a system reaching equilibrium when you begin with  reactants only,  and
then again when you begin with only products.  This lab will help you identify when a system has reached 
equilibrium & what the concentration of the reactants and products are at equilibrium.  Upon completion of this lab,
you will have completed objective 2. 
 
 

  C. Culminating & Assessing Activity : 

              3.  Graph the results of the  Establishing Equilibirum lab.   Plot the concentration of both the [ R ] and [ P ] 
(on the y-axis)  versus the number of transfers  (on the x-axis).   The data  for each  [ R ]  and  [ P ]    must be represented
by  a different  colored line. 
 

  Homework:     1)  Complete graph, 
                                     2)  Write-up  the  Chemical Equilibrium: Qualitative Aspects (Ferric thiocyanate Lab) 
                                          procedure,  ( page 2 of lab activities, Unit 10 )         and 
                                     3)  Complete reading handout -  Ch. 11 through and including 11-2.3). 
 
 
 
 

  Day 3   ( Special block schedule - 2 hour classes ) 
 

  A. Review: 

              1.  After comparing your graph with the rest of the class and data on the ASAP CHEM! CD ROM,
you will determine what conditions had to exist, in the lab activity, in order for you to know that equilibrium was indeed established. 

       B. Introductory Activity: 

              2.  After observing a Powerpoint Presentation (Slides 1 - 5) and completing a lab called: Chemical Equilibrium: Qualitative Aspects, you will be able to complete objective 3:  Students will be able to define LeChatelier's Principle. 

  C. Enabling Activities: 

              3.  Complete  part 1 (steps 1 -4) of Chemical Equilibrium: Qualitative Aspects  and write the equation for the reaction. 

  Homework : 1)   Read 11-3 through 11-5.4 
 
 
 
 

  Day 4   ( Regular schedule ) 
 

  A. Enabling Activities continued: 

              1.  Complete  lab:  Chemical Equilibrium: Qualitative Aspects.

  B. Assessing Activity: 

  Homework :    1)  Complete lab questions 1 -11. 
                                            2)  Lab due:  procedure, data, questions. 
 
 

  Day 5 ( Regular schedule )
 

  A. Introductory Activity:

              1.  After observing and discussing the following demonstration and reviewing LeChatelier's Principle through a Powerpoint  Presentation, (Slide 6 & 7) you will be able to complete part of Objective 4:  Students will be able to use LeChatelier's Principle to predictthe effect of  changing the concentration of a system at equilibrium. 

  B. Enabling Activities:

              2. Observe, predict the outcomes and  discuss the following demonstration. 
  Demonstration:  LeChatelier's Principle  &  Concentration 

                               Co(H2O) 6 2+(aq)   +  4  Cl- (aq)  =  CoCl42- (aq)  +  6 H2O (l) 
                                    (pink)                                           (blue) 

             What will happen when you  add:
                                                                   20 mL  pink + HCl? 
                                                                   20 mL blue + water? 
                                                                   20 mL blue + AgCl ? 

  C. Assessing Activity: 

                Homework :   1)  Complete the LeChatelier's review  worksheet. (page 3 of lab activities, Unit 10) 
 
 

  Day 6 ( Regular schedule )
 

        A. Introductory Activity: 

              1.  After observing and discussing the following demonstration and reviewing LeChatelier's Principle you 
will be able to complete another part of  Objective 4:  Studentswill be able to use LeChatelier's Principle to predict the effect
of changing the temperatureof a system at equilibrium. 

       B. Enabling Activities:

              2. Observe the following demonstration so as to predict which side the energy term belongs on. 
Demonstration:  LeChatelier's Principle  & Temperature 
                              Co(H2O) 6 2+(aq)   +  4  Cl- (aq)  =  CoCl42- (aq)  +  6 H2O (l) 
                                    (pink)                                           (blue) 

                                                                   50 mL of control (purple) at room temperature 
                                                                   50 mL  of purple +  hot water bath (turns blue) 
                                                                   50 mL of purple + cold water bath (turns pink) 
 

  C. Culminating Activity : 

              3.  Review  LeChatelier's Principle with the   ASAP CHEM!  CD Rom. 
 

  D. Assessing Activity : 

  Homework:     1)  Complete second LeChatelier's Principle worksheet (page 4 of lab activities, Unit 10)
                                            2)  Begin Equilibrium & LeChatelier's Principle study guide (1 - 19)
 
 

  Day 7 ( Regular schedule ) 
 

  A. Introductory Activity:

              1.  After observing and discussing the following demonstration and reviewing LeChatelier's Principle you 
will be able to complete the pressure & volume portion of  Objective 4:  Students will be able to use LeChatelier's Principle to predict the effect ofchanging the pressure and volume of a system at equilibrium, 

  B. Enabling Activities: 

              2. Observe the following demonstration so as to predict which reaction is favored with an increase in pressure, and  an increase in volume. 

                 Demo:    Pressure and Volume Changes on Carbon dioxide/Carbonic Acid Equilibrium. 

                                            2 H2O    +   CO2    =     H3O+   +    HCO3-
                                               ( yellow )                                ( red ) 

      C. Culminating Activity : 

               3.  You will review  LeChatelier's Principle by participating in a virtual lab on line.   In class,  we will use
the LCD projector to complete a sample prelab, experiment, and  postlab set,  found at:
  http://www.capital.net/com/vcl/equil/equil.htm
 

  D. Assessing Activity : 

                   Homework:     1)  Complete one review and one new  virtual experiment online at: 
                                                            http://www.capital.net/com/vcl/equil/8perform.htm
                                                   a. While at the introduction page, click on the lower left icon for a page listing of 
                                                       topics .  This will take you to the page listing for the site. 
                                                   b. Complete the cobalt system (as review)  and then choose one of the following 
                                                       systems to complete:  ammonium, chromate or copper sulfate. 
                                                2)   Read  11-6 through 11-7.2 
 
 

  Day 8 ( Regular schedule ) 
 

         A. Introductory Activity: 

              1.  After reviewing the homework, you will participate in a discussion  & problem solving session involving the quantitative study of equilibrium.   This will allow you to complete Objective  5:  Students will be able to write the equilibrium law expression for areaction, and   Objective 6:  Students will be able to complete calculations based on  Keq.
 

          B. Enabling Activities: 

               2. You will write the Equilibrium Law Expression for the sample problems given in class. 

           C. Assessing Activity : 

  Homework:   1)  Complete study guide (20 -21) 
                            2)  Write up the procedure  for the Chromate - Dichromate Equilibrium Lab  (page 5 of lab 
                                     activities, Unit 10)
 
 
 
 
 
 

  Day 9 ( Regular schedule ) 

  A. Culminating Activity :     The Chromate - Dichromate Equilibrium
 

                 1. Complete the Chromate - Dichromate Equilibrium experiment. 

  B. Assessing Activity : 

                 2. If the equilibrium equation for this reaction is, 

                                                                2 H+(aq)  +  2 CrO42-(aq)  =  Cr2O72-(aq)  +  2 OH-(aq) 

   then,  using  LeChatelier's Principle,  predict the results of adding H+,  OH-  and  Ba2+ to the system. 

  Homework:  1) Complete final activity ( Turn in procedure, data and predictions )
                           2) Study for exam 
                           3) Homework packet due the day of exam 
 
 
 
 
 
 

Assessment

To view the Rubric for the Culminating Activity - The Chromate - Dichromate Equilibrium Lab
click on rubric.  ( 30 points total )
 

Results
 

     For a comparison of culminating activity success and post-test performance,   click   here.

     For a comparison of pre-test, post-test, and culminatiing activitiy performance,  click  here.
 
 

Web Resources & Supplementary Materials
 
 

      
California State Framework :   http://scorescience.humboldt.k12.ca.us/fast/teachers/content/hschem.htm

 
Copies of Pre-test, Post-test, and Study Guide :  Materials Page
 

Background, virtual labs resources :  http://www.capital.net/com/vcl/equil/equil.html
 
 
 
 
 
 
 


 
 
 
 
 
 
 
 
 
 
 
 
 

School Name: Independence High School 
School Location:  1776 Educational Park Dr., San Jose, CA  95133
Your Name and e-mail address:  Leslie W. Bailey     school e-mail:  baileyl@esuhsd.com 
Last Revised: 07/24/2001