Objectives:                   Students will be able to describe a dynamic equilibrium exists regardless   of concentration levels

Hendricks, Richard

English

The College at Brockport, State University of New York: Digital Commons @Brockport

The College at Brockport: State University of New York
Digital Commons @Brockport
Lesson Plans CMST Institute
9-16-2006
Relationships in chemical equilibriums
Richard Hendricks
The College at Brockport
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Hendricks, Richard, "Relationships in chemical equilibriums" (2006). Lesson Plans. 59.
http://digitalcommons.brockport.edu/cmst_lessonplans/59
Hendricks  Group K CMST 2006  
Richard Hendricks 
 
Subject taught: AP chemistry 
 
Topic: Relationships in chemical equilibriums 
 
Objectives:  
Students will be able to describe a dynamic equilibrium exists regardless of concentration levels.  
 
 
Key Ideas and standards: 
Chemical equilibrium exists when there is no longer a change in concentration.  Many students confuse 
equilibrium with the concept of equal concentrations. If reactant A is needed to form product B and 
product B is needed to run backwards to form reactant A, an equilibrium will be established when A 
forms B at the same rate that B forms A.  This will not necessarily lead to equal concentrations.   
 
If equilibrium exists in a fish tank which leaks into a cup.   The fluid levels in the tank and the cup may 
never be the same, but overtime, the cup must be dumped (or pumped ) back into the tank.  
Equilibrium occurs when it is pumped back into the tank at the same rate the tank leaks.   
 
To model this, we could use yellow and blue agents.  As the animation takes place, the yellow agent 
takes on 20 % chance of turning blue.  The blue agent has a 60% chance of turning yellow.  Over time, 
we expect that an equilibrium will develop regardless of initial conditions.    It may start off all blue 
and quickly turn to yellow or start off all yellow and turn blue.  Either way, the equilibrium point is 
established by the probability that one color will turn into another.  Obviously, if there is no blue, the 
blue cannot make any yellow and vice-versa.  
 
 
Materials: 
Agents sheets software.   
 
Description 
Make an agent sheet with two agents – a blue and a yellow.  Adjust the behavioral conditions for each 
agent so that whenever a blue agent is next to a yellow one, the agent has a 60% chance of turning into 
the yellow agent.  Make the yellow agent have a 20% chance to turning blue.  Start with a variety of 
starting positions.  Make half yellow, half blue,  100 % yellow, 100 blue and so forth.  Run the 
simulation until it reaches equilibrium.   If the agents are small enough the yellow and blue make form 
the same shade of green.  With bigger agents, you should find equilibrium when the color changes 
occur constantly but produce no “net result” 
 
 
Questions to answer: 
 
1) How is the time it takes to reach equilibrium affected by the initial condition?  Does it reach 
equilibrium faster when it is 100 % yellow or 100% blue.   
2) At what size agent is it hard to tell when equilibrium occurs? 
3) Several measures indicated that unless you have 10 x as many of one color molecule than the 
other, it is difficult to tell  which molecular form predominates. Does it appear that same 
argument is true for  agents? 
4) In molecular terms, why is it impossible to have equilibrium established when the 
concentration of one of the reactants is zero? 
5) When the concentration is of a reactant or product is given in an equation as ( X – 0.07)M, 
what is the largest value of X possible?  Likewise , sometimes you solve ( X + 0.006)M, for 
concentration.  What is the limit on X in this case? 
 
  
 
 
Assessment and evaluation 
 
5 points  3 to 4 points 1 to 2 points 
Student completes the 
simulation with all 
questions answered 
properly in clear, coherent 
english 
Student completes 
approximately 75 % of the 
agent with partial answers 
to all questions.   
Student attempts to make 
the agentsheet without 
results.  Does few or not 
questions.    
 
  


Relationships in chemical equilibriums

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Relationships in chemical equilibriums

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