Last modified: Thu 02/26/2009 09:32:45 am
ACA for Extent of a Reaction

Shifting Reactions A After Class Application activity.

Answer all of the questions below. If you do not know an answer enter CNA. However, it will help me the most if you answer each question with your best intuition/idea about what would be a reasonable answer.

First Name:

Last Name:

Laboratory Section:

In this activity you will determine the magnitude of the equilibrium constant for a chemical reaction.

In this exploration you will collect some experimental data for a chemical reaction. Click here to bring up a new window with the simulation.

The reaction we are investigating in this simulation is

R + G ---> RG

a) In the Table I below enter the amounts of R, G, and RG into the cells in the Initial Concentration (the second) row.

Experiment #1 R + G --> RG
Initial Concentration - I  
Concentration Change - C  
Ending Concentration - E  

Table I.

Next, in the simulation window for the reaction, click on the Resume Button then click on the Enable Reactions button. When you feel the reaction is complete click the Pause button.

b) Record the amounts of R, G, and RG in the Ending Concentrations row in Table I.

c) Determine the change in concentration for R, G, and RG and enter the amounts in the Concentration Change row Table I.

d) Write the equilibrium expression for the reaction.

K =

e) Calculate the magnitude of the equilibrium constant for the reaction.

K =

2. Reset the simulation by clicking on the Reset button. For Experiment #2 you may use any initial amount for R, G and RG between 0 and 1.00 mol. Changing the initial amount can be accomplished by either sliding the ControlBar for each reactant and product, or by clicking on the amount and typing in the new amount and pressing the Enter key on the keyboard.

a) In the Table II below enter the amounts of R, G, and RG into the cells in the Initial Concentration (the second) row.

Experiment #2 R + BG --> RG
Initial Concentration - I  
Concentration Change - C  
Ending Concentration - E  

Table II.

Next, in the simulation window for the reaction, click on the Resume Button then click on the Enable Reactions button. When you feel the reaction is complete click the Pause button.

b) Record the amounts of R, G, and RG in the Ending Concentrations row in Table II.

c) Determine the change in concentration for R, G, and RG and enter the amounts in the Concentration Change row Table II.

d) Write the equilibrium expression for the reaction.

K =

e) Calculate the magnitude of the equilibrium constant for the reaction.

K =

3. Summarize the effect changing the initial concentration of reactants and products (based on the responses in Question 1 and Question 2 above) has on the magnitude of the equilibrium constant for the reaction.

4. Reset the simulation by clicking on the Reset button. For Experiment #3 you are to use the same initial amounts as used in Experiment #1 above.

a) In the Table III below enter the amounts of R, G, and RG into the cells in the Initial Concentration (the second) row.

Experiment #3 R + BG --> RG
Initial Concentration at 400 K - I  
Concentration Change at 400 K - C  
Ending Concentration at 400 K - E  

Table III.

b) In the reaction window look at the reaction profile in the lower right corner of the page. Is this reaction endothermic or exothermic?

c) Based upon Le Chatelier's Principle and the results from Question 1 above, predict what will happen to the concentration of the reactants and products at equilibrium as a result of increasing the temperature of the reaction.

Concentration of R : increase, decrease, or remain the same as the ending amount in Question 1

Concentration of G : increase, decrease, or remain the same as the ending amount in Question 1

Concentration of RG : increase, decrease, or remain the same as the ending amount in Question 1

Having made your predictions, go to the simulation window for the reaction, and increase the Temperature, by sliding the ControlBar, to 400 K. Now click the Resume Button then click on the Enable Reactions button. When you feel the reaction is complete click the Pause button.

b) Record the amounts of R, G, and RG in the Ending Concentrations row in Table III.

c) Determine the change in concentration for R, G, and RG and enter the amounts in the Concentration Change row Table III.

d) Write the equilibrium expression for the reaction.

K =

e) Calculate the magnitude of the equilibrium constant for the reaction.

K =

5. Summarize the effect increasing the temperature of this chemical reaction (based on the data in Table I and Table III above) has on the magnitude of the equilibrium constant for the reaction.

6. Predict how the magnitude of the equilibrium constant changes for an increase in temperature for an exothermic reaction.

(increase, decrease or no change)

7. Is there anything about the questions that you feel you do not understand? List your concerns/questions.

8. If there is one question you would like to have answered in lecture, what would that question be?