Visual Simulation of Chemical Equilibrium
This simulation will help you visualize a reaction such as:
2NO2(g) ↔N2O4(g)
where NO2 molecules are represented by red dots and N2O4 molecules are represented by
blue dots. Two red dots collide to form one blue dot (N2O4), and a colliding blue dot
produces two red dots (NO2).
A. Reaching Equilibrium
1. Set Red number (RN) to 39 and Blue Number (BN) to 0. Click “Equilibrate.”
Wait until numbers stabilize, then wait a bit longer to be sure.
At equilibrium, RN = ______ and BN = ______
2. Click “Reset,” then set RN to 0 and BN to 19. Note that this is the REVERSE of
#1.
At equilibrium, RN = ______ and BN = ______
3. What do you conclude about the effect on equilibrium of the DIRECTION from
which it is approached?
B. Effect of Temperature in Attaining Equilibrium
1. Set RN = 39 and BN = 0
2. Set “Temperature” to 1K, click “Equilibrate” and time how long the system takes
to reach equilibrium.
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3. Reset to RN = 39 and BN = 0, but increase the temperature as indicated in the
following table: (You may need to use the arrows, < and > to get the exact
temperatures.)
Temperature (K)
Time to Reach Equilibrium (s)
1
5
20
100
200
4. What is the relationship between temperature and how long it takes to reach
equilibrium? Explain why this makes sense.
C. Effect of Probability of Reaction from a Collision
The probability of a collision resulting in a reaction depends on temperature (average
speed of the molecules), the angle of the collision, and how strong the bonds are that
hold the atoms together in a molecule. For each trial below, reset RN = 39 and BN =
0, keep the temperature at 273 K, and leave the Red Probability = 0.5 (50% of all
collisions will turn the reds into blues.) Incrementally decrease the probability of the
reverse reaction by setting the Blue Probability lower for each trial, according to the
table below:
Trial
1
2
3
4
5
Blue Probability
0.5
0.4
0.3
0.2
0.1
RN
BN
As the reverse reaction probability decreases (compared to the probability of a
forward reaction), what is the effect on the equilibrium position 9proportions of
reactants and products)?
2