Chemical Equilibrium Game: Work in a group of 2
Chemical Equilibrium is defined as a state of reaction where the rate of change in the reactants and the
products remains constant. Note that the amounts of the different entities need not be constant, only their
respective rates of change.
Because many chemical equilibria take place in the gaseous or aqueous phase, it is almost impossible to
see the constant reaction that is going on, and to the naked eye, there appears to be no reaction. This is
the phenomenon of equilibrium, and it is extremely vital to how our modern society functions.
Luckily, there is a solution which exists that can show how equilibrium actually occurs, and the only
supplies that are required are a pair of graduated cylinders, some drinking straws, and some basic tap
water.
Purpose: the purpose of this demonstration is to decide what equilibrium is for a simple system.
Procedure: Fill one graduated cylinder with 25 mL of water, and leave the other cylinder empty. Then
have two people each take a drinking straw, but ensure that the two straws have different radii, and drop
them into the graduated cylinders. Each person should then plug the top end of the straw with their
thumb, so as to create a pseudo-vacuum, and then each person should transfer the amount of liquid they
pick up to the other cylinder. Note that the first time, there will be no exchange from the empty
cylinder. For each subsequent trial, the volume of the water in the cylinders will change by a differing
number, because the amount of water picked up is dependent upon how much water is already in the
containers.
Record the volume of each cylinder after every 3 transfers (remember that both volumes should combine
to a total of 25 mL). After a while, you’ll notice that equilibrium has been achieved, as the volume in
either cylinder will not change regardless of how many transfers are performed. After you have recorded
3 consecutive values you should stop.
Observations:
Number of Transfers
Volume in A (mL)
Volume in B (mL)
Analysis:
1. Graph the number of transfers vs Volume of A and volume of B on the same axis. Join each line
with the curve of best fit.
2. Describe the changes both in volume (simulated concentration) and corresponding rates which
occur in each of the curves up to the point of equilibrium.
3. If the wide tube was used in cylinder A, then at equilibrium the larger volume should be in
since if the forward reaction is favoured .
4. What is equal about equilibrium?
5. Under what condition would you expect to find equal volumes in A and B at equilibrium?
6. What chemical situation (what type of system) might this represent?