Exploring Le Chatelier’s Principle Simulation Lab

Lab Write-up: Answers to questions, graphs, data table. Group Names

PART A: Effect of temperature on Equilibrium Login to the computer and open a web browser. Go to http://phet.colorado.edu. Click “Play with Sims,” then find the “Chemistry” section, and choose “Reactions and Rates.” When the simulation is open, click on the “Rate Experiments” tab.

Look at the screen and observe everything you can find out about the reaction pictured, A + BC  AB + C with yellow A and purple/blue BC reactants. Click on the “Strip” Chart Options in the Options box on the lower right hand corner.

1) What type of reaction is it? Is it endo or exothermic?

2) Predict what will happen when 80 A’s are added to the box and 80 BC’s are added.

3) In the box labeled “Initial Conditions,” enter 80 for A and 80 for BC. Click “Begin experiment”. Wait until equilibrium is achieved. a) Was your prediction correct? Describe and explain any differences. Provide numerical data to support your claims.

b) Describe the nature of dynamic equilibrium when small numbers of particles (e.g. 80 compared to 6.022 x 1023) are present.

4) Predict what will happen when the temperature is raised at equilibrium so it is NOT above the activation energy max but IS above the energy level of the products.

1 5) Raise the temperature as described. Did your prediction come true? Describe and explain any differences. Provide numerical data to support your claims.

6) Predict what will happen when the temperature is raised so it is above the activation energy max.

7) Raise the temperature as described at equilibrium. Again, was your prediction correct? Describe and explain any differences. Provide numerical data to support your claims.

8) What did you notice about the rate at which reactants/products fluctuated between the three different temperatures? If you didn’t notice anything, hit “reset all” and test it again.

9) Did temperature affect equilibrium position? Did it affect it in the way you expected? Explain.

10) Did temperature affect reaction rate? Did it affect it in the way you expected? Explain.

2 PART B: Effect of concentration on Equilibrium Login to the computer and open a web browser. Go to http://phet.colorado.edu. Click “Play with Sims,” then find the “Chemistry” section, and choose “Reactions and Rates.” When the simulation is open, click on the “Rate Experiments” tab.

Look at the screen and observe everything you can find out about the reaction pictured, A + BC  AB + C with yellow A and purple/blue BC reactants. Click on the “Strip” Chart Options in the Options box on the lower right hand corner.

1) In the box labeled “Initial Conditions,” enter 80 for A and 80 for BC. Click “Begin experiment”. Wait until equilibrium is achieved. 2) Click “Pause” 3) Double of amount of “C” present in “Current Amounts” 4) Predict what will happen to equilibrium when the concentration of reactant C is doubled.

5) Click “Play”. Was your prediction correct? Describe and explain any differences. Provide numerical data to support your claims.

6) Click “Reset”. Start again with 80 A and 80 BC. Click “Begin experiment”. Wait until equilibrium is achieved. 7) Click “Pause” 8) Reduce the amount of “C” present in “Current Amounts” by 50%. 9) Predict what will happen to equilibrium when the concentration of C is reduced.

10) Click “Play”. Was your prediction correct? Describe and explain any differences. Provide numerical data to support your claims.

3