Reactions and rates phet answers

Phet Simulation: Reactions and Rates
Name:

PART A. Exploring Equilibrium

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image1.png In this lab activity you will use a PhET simulation (University of Colorado) to explore concentration. You will be running the Java Simulations powered by Cheerp J so that is can run in your web browser. Go to the following website to access the PhET simulation: https://docs.google.com/document/u/1/d/e/2PACX-1vQGvm1uzGzSvzLOpd61QETqHaDOQnOvDc3TtlhqDQxAjahpj6HBrU3UrLtHfUJ1nDJk9IjUv-WcRxab/pub

Scroll down and select “Reactions and Rates”. When the simulation is open, click on the “Many Collisions” tab.

Look at the screen and observe everything you can find out about the reaction pictured, A + BC ( AB + C.

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

2) Predict what will happen when 50 A’s are added to the box and 50 BC’s are added.

3) In the box labeled “current amounts,” enter 50 for A and 50 for BC.

a) Was your prediction correct? Describe and explain any differences.

b) Describe the nature of dynamic equilibrium when small numbers of particles (such as 50, as compared to 6.022 x 1023) are present.

4) What is Le Châtelier’s Principle? How do you think it relates to this simulation?

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

6) Raise the temperature as described. Did your prediction come true? Describe and explain any differences.

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

8) Raise the temperature as described. Again, was your prediction correct? Describe and explain any differences.

9) 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.

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

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

12) Write the equilibrium expression for this reaction. Because of the way the numbers fluctuate, it would be hard to calculate the equilibrium constant, but how would you do it if the numbers ever settled down?

PART B: Le Châtelier’s Principle
Choose the “Rate Experiments” tab. As you play with the sim, answer the questions below.

1. A. In the previous lab (“Exploring Equilibrium”) you investigated the effect of temperature on equilibrium position; you may have found that temperature did not affect equilibrium in quite the way you expected. Add 80 A’s and 80 BC’s to the box for the first reaction and begin the experiment; let the reactions run until equilibrium is reached. (Reaction #1)Knowing Le Châtelier’s Prinicple, now predict and explain what will happen to the equilibrium position when the temperature is raised and lowered. Copy and paste the energy diagram for this reaction and use it to explain your results.

B. Then test your ideas using the sim and explain your observations. Give numerical data to support your claims. (At the end of the experiment, what are the amounts of A’s, BC’s, AB’s and C’s present)

2. There are three other reactions you can play with under the “Select a Reaction” menu. For each of the three other

reactions, predict what will happen to the equilibrium position when the temperature is raised or lowered. Be sure to

explain the differences between the four reactions. Test your ideas using the sim; give numerical data to support your

explanations. (What are the amounts of A’s, BC’s, AB’s and C’s present)

Copy and paste the energy diagrams that corresponds to each of the reactions.

A. Reaction #2:

B. Reaction #3:

C. Reaction #4:

3. Reset the simulation and return to the first of the four reactions. Begin with 50 A’s and 50 BC’s and let the

simulation run to equilibrium.

A. Predict what will happen to the equilibrium position when more BC’s are pumped into the container.

B. Test your ideas using the sim and explain your observations. Give numerical data to support your claims.

(What are the amounts of A’s, BC’s, AB’s and C’s present)

4. Assuming this reaction is taking place in the gas phase, what would be the effect on equilibrium position of increasing the pressure inside the container?