Project: Equilibrium Simulation

Transcription

1 UNIT 02: BCLN CHEMISTRY 12 - Rev. July, 2015 Project: Simulation Potential Credits: /20 Name: Goal: In this project you will explore the concept of reversible reactions and calculating K eq using some simulated reactions. You will also explore how changing temperature affects K eq. Instructions: Before you begin be sure you have an updated version of java. This can be downloaded at: Java Once you have java installed, begin by opening the simulation at the following link: Reaction Rates You will be required to download a file and then open it. When done correctly you should see the following screen: Page 1 of 8

2 UNIT 02: BCLN CHEMISTRY 12 - Rev. July, 2015 Single Collisions: 1. Pulling down on the red plunger will cause the green line in the energy diagram to move upward. Releasing the plunger will cause the yellow atom to shoot up at the purple/blue molecule. Pull the plunger to maximum, release and describe what happens inside the box. 2. In order to have an equilibrium the reaction you are looking at must be reversible? Is the A + Bc reaction reversible? Explain. K eq Calculation Experiment: 1. Press the blue tab at the top of the screen that reads: Start by setting the A and Bc to have 100 each. Click the Bar button and the Show stopwatch. Your screen should now look like the following: Page 2 of 8

3 UNIT 02: BCLN CHEMISTRY 12 - Rev. July, When you look at the Energy vs. Reaction Coordinate graph, which side of the reaction has higher potential energy, the reactants or the products? 3. Is this reaction exothermic or endothermic? Explain how you know this. 4. Do you expect the reactants or products to be favored in this reaction? Explain why. 5. Assuming entropy does not change in this reaction and based on your answer to the above question predict whether K eq will be less than 1 or greater than 1? Explain why. 6. We are going to use the simulation to try and determine a K eq value for this reaction. Be aware that numbers may vary so do not panic if your K eq values vary. Double check that you have set A to 100 and Bc to 100. Click Begin Experiment and Start on the stopwatch. Let the experiment run until the stopwatch hits This should be enough time to let an equilibrium establish itself. At 2000 hit End Experiment and record the values for each molecule in the table below. Be very careful not to adjust the temperature at any time. Trial 1 A Bc AB c Original Amounts Normally we use concentration to calculate K eq. In this case since we are leaving the size of the box the same for all of our experiments we can simply use the Amounts to calculate K eq. The K eq equation for this reaction is: K eq = (Amount AB)(Amount c) (Amount A)(Amount Bc) Calculate K eq using the equilibrium values you recorded in the table above 8. Repeat the experiment and K eq calculation for each of the following initial values given below and on the next 2 pages. Page 3 of 8

4 UNIT 02: BCLN CHEMISTRY 12 - Rev. July, 2015 Trial 2 A Bc AB c Original Amounts Trial 3 A Bc AB c Original Amounts Trial 4 A Bc AB c Original Amounts Trial 5 A Bc AB c Original Amounts Trial 6 A Bc AB c Page 4 of 8

5 UNIT 02: BCLN CHEMISTRY 12 - Rev. July, 2015 Trial 7 A Bc AB c Original Amounts Trial 8 A Bc AB c Original Amounts Trial 9 A Bc AB c Original Amounts Trial 10 A Bc AB c Original Amounts Trial 11 A Bc AB c Page 5 of 8

6 UNIT 02: BCLN CHEMISTRY 12 - Rev. July, 2015 Original Amounts Trial 12 A Bc AB c Original Amounts Calculate the average K eq using the values from the 12 trials you have done. Average = K eq Calculation Questions: 1. Did the K eq you calculated fit with the prediction you made earlier (question 5 in previous section)? 2. You calculated the K eq for the forward reaction above. What is the K eq for the reverse reaction? 3. Use the average Keq you calculated in the Experiment section to answer this question. If the amounts of A, Bc and AB are all found to be 50 at equilibrium, calculate the amount of c that should be present. Page 6 of 8

7 UNIT 02: BCLN CHEMISTRY 12 - Rev. July, Test these values in the simulation. Is there any large change over time? Why or why not? K eq Temperature Experiment: 1. As the finale to this project you will do an experiment to determine the effect of temperature on K eq. Begin by predicting the effect on the K eq of raising the temperature and explain you reasoning. Hint: Is the forward reaction Exothermic or Endothermic? 2. For this part of the experiment you will always use 50 for all four molecules. Instead of changing the amounts you will change the temperature. Start with the temperature at the default setting. Run the simulation, fill in the equilibrium amounts in the table and calculate K eq. Temp 1 A Bc AB c 3. Slide the temperature bar to the right so it lines up with the r in temperature as shown in the diagram. Page 7 of 8

8 UNIT 02: BCLN CHEMISTRY 12 - Rev. July, 2015 Temp 2 A Bc AB c 4. Slide the temperature bar further right so it is just past the e as show in the diagram. Temp 3 A Bc AB c 5. Slide the temperature bar further right as shown in the diagram. Temp 4 A Bc AB c 6. What is the general trend for K eq as the temperature is raised. Does this match with your prediction in question 1? Page 8 of 8