Chem Lab 2013 Institute
Equilibrium Hands-On Demonstration
Experiment 1: R starts with 40, P starts with zero.
Consider the following simplified equilibrium: R
Round to whole numbers!
P
R transfers ½ of their items, P transfers ¼ of their items
Number of
Number
Number of
items, R
transferred to P items, P
Start
40
XXXXX
0
1st transfer
XXXXX
XXXXX
Outcome 1
XXXXX
nd
2 transfer
XXXXX
XXXXX
Outcome 2
XXXXX
rd
3 Transfer
XXXXX
XXXXX
Outcome 3
XXXXX
4th Transfer
XXXXX
XXXXX
Outcome 4
XXXXX
th
5 Transfer
XXXXX
XXXXX
Outcome 5
XXXXX
6th Transfer
XXXXX
XXXXX
Outcome 6
XXXXX
th
7 Transfer
XXXXX
XXXXX
Outcome 7
XXXXX
8th Transfer
XXXXX
XXXXX
Outcome 8
XXXXX
Number
transferred to R
XXXXX
XXXXX
XXXXX
XXXXX
XXXXX
XXXXX
XXXXX
XXXXX
XXXXX
1. Once equilibrium was reached, what was the same for both P and R sides?
2. What is the value of the equilibrium constant for this reaction?
Chem Lab 2013 Institute
3. Graph number of products vs transfer and number of reactants vs. Transfer.
Experiment #2. What happens when the equilibrium is disturbed? Start this experiment with
your numbers of items from when you reached equilibrium.
Number of
items, R
Start
Stress
Result of Stress
1st transfer
Outcome 1
2nd transfer
Outcome 2
3rd Transfer
Outcome 3
4th Transfer
Outcome 4
+20
XXXX
XXXX
XXXX
XXXX
Number
Number of
transferred to P items, P
XXXX
XXXX
+0
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
Number
transferred to R
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
4. Experiment 2 featured a shift in the equilibrium. Did all the extra items stay in the reactants or
did some “shift” to the products. What was the equilibrium constant at the end of this
experiment?
5. Calculate the reaction quotient Q at the “Result of Stress” Line. How does the value of Q
compare to K? How could you have used this to predict the direction of the shift?
Chem Lab 2013 Institute
Experiment #3. What happens when the equilibrium is disturbed again? Start this experiment
with your numbers of items from when you reached equilibrium in Experiment #1.
Number of
items, R
Start
Stress
Result of Stress
1st transfer
Outcome 1
2nd transfer
Outcome 2
3rd Transfer
Outcome 3
4th Transfer
Outcome 4
-10
XXXX
XXXX
XXXX
XXXX
Number
Number of
transferred to P items, P
XXXX
XXXX
+0
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
Number
transferred to R
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
XXXX
6. Experiment 3 featured another shift in the equilibrium. Did the deficit remain in the reactants
or did some of the products “shift” to replace what was lost in the reactants. What was the
equilibrium constant at the end of this experiment?
7. Once again, calculate the value for the reaction quotient, Q, at the “Result of Stress” line. How
does your value of Q compare to K? How could you have used this to predict the direction of the
shift?
8. Given the fact that you are rounding whole numbers to get equilibrium, where the three
equilibrium constants relatively close to each other? Would you conclude the equilibrium
constant should remain “constant” once equilibrium is reached, regardless of starting
concentrations?