Dynamic Equilibrium Simulation Lab
Purpose:
1. To understand how and why equilibrium is established
2. To define equilibrium position and equilibrium constant
3. To identify factors that affect the equilibrium constant, the equilibrium position, and the time it takes to reach equilibrium.
Introduction:
We will be modeling the reaction:
P + P D P2
by putting paper clips together (forward reaction) and taking them apart (reverse reaction). This simulation allows us to “Stop” the reaction after a certain amount of time so that we can monitor the “concentrations” of the reactants and products. This is obviously much more difficult to do with a real chemical reaction so it is up to you to think about how the paper clips relate to a real chemical reaction.
In order to simulate this reaction, we will need to simulate the forward reaction and the reverse reaction.
a. Why do we need to simulate the reverse reaction? (Explain using collision theory)
b. Why will it be necessary for the person putting paper clips together to do so at a constant rate?
c. What would it represent if the person putting paper clips started putting them together faster?
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d. How will we know that equilibrium has been established?
e. Challenge: How would we simulate adding a catalyst? How would we simulate increasing temperature?
Procedures:
PART I: Establishing Dynamic Equilibrium
1.1 Start with 48 paper clips. Each group will be three people doing the reaction and one person timing. Two people will put paper clips together. One person will take paper clips apart.
1.2 Everyone should begin as soon as the timer starts. Time for 10 seconds, stop, record the number of free paper clips and the number of paper clip molecules.
1.3 Calculate Keq
1.4 Graph your data (remember to label properly).
1.5 Answer question 3.1 and 3.2 then go to part 2
PART 2: Factors that Affect Equilibrium
Do other rounds in which you
2.1 Have two reverse reactors and one forward reactor
2.2 Have reactors, reacting as fast as they can (What does this simulate?)
2.3 Have someone constantly removing P2 as it gets made
2.4 Start with only P2 molecules
2.5 Have someone arbitrarily start adding more paper clips
2.6 Have someone arbitrarily start adding more P2 molecules.
2.7 Finish the analysis questions.
PART 3: Analysis:
3.1 How does the rate at which the paper clips are put together change with time? Explain in terms of collision theory. How does the rate at which the paper clips are taken apart change with time? Why?
3.2 Define dynamic equilibrium. Does equilibrium mean that there is the same amount of reactant and product?
3.3 One person in each group should choose one of the extra rounds to analyze. You should compare your extra round (one of the round in part 2) to the first round (part 1). Talk about the rate at which equilibrium was reached or if it was reached. Explain the differences using collsion theory. Also, identify what your extra round is simulating. Talk about the relative stability of reactants and products.
3.4 Assume that paper clips are RED, but P2 molecules are blue. What color are the equilibrium solutions for 2.1 to 2.6 (ignore any that don't come to equilibrium)?
a. Why do we need to simulate the reverse reaction? (Explain using collision theory)
b. Why will it be necessary for the person putting paper clips together to do so at a constant rate?
c. What would it represent if the person putting paper clips started putting them together faster?
A faster reaction rate...could be increased surface area, could be increased temp, but then the reverse would also need to increase.
d. How will we know that equilibrium has been established?
e. Challenge: How would we simulate adding a catalyst? How would we simulate increasing temperature?
Increasing temperature requires you to know whether the reaction is exothermic or endothermic. Assuming you thought the reaction was exothermic, it would be necessary for both forward and reverse to speed up, but for the reverse to speed up more...hard to simulate.