Online Chemistry 11 Lab #16

 

Reaction Equilibrium

This will work best in groups of three with each of you in a particular role:

1. One of you will need a stopwatch and will be in charge of timing and noting data.
2. One of you will be joining single pieces of Lego into doubles.
3. The last of you will be breaking up double Legos into singles).

This also works better if person B and C don’t try racing each other, but simply carry out their tasks at a steady pace. This will prove easier if you close your eyes.

 

Theory: Write a reversible reaction equation for your particular “reaction.”   (For the disco example I wrote:  line up people <–––> disco people.)

Write an expression for the equilibrium constant for your “reaction.”  (For the disco example I would write: K_eq =[disco people]/[line up people].)

Discuss what will remain constant at equilibrium.  Write out Le Chatelier’s Principle.

 

 
Measuring the Equilibrium Constant for Joining Lego

1. Place the Lego on the lab bench in single pieces.  Count them.  Try to get same size pieces and about 100 in total.
2. Person A should reset the stopwatch to zero and fill in the first data point in a table with headings: Time, # Singles, # Doubles.   
3. Person A will call “Start” and members B and C begin to join/unjoin.
4. Every 15 seconds Person A will call “Stop” and do a count and fill in the data.
5. Proceed like this for about 3 minutes or at least until equilibrium appears to have been reached plus one minute.
6. Graph your results:  on one graph plot time on the x-axis and # singles/doubles on the y-axis (this gives two graphs, one for singles and one for doubles).
7. Does equilibrium appear to have been reached? 
8. Calculate your equilibrium constant.
9. Redo the experiment from 1 but starting with all Legos joined.  Don’t bother re-graphing but do calculate the K_eq again.
10. Now try it with all singles but only have half as many as before.  Predict what you expect the equilibrium point to be and compare it to your results.  (Use the average of the two K_eq s for this.)  Do they agree?

 

Investigating Le Chatelier’s Principle by Joining Lego

1. Still using half the of Legos run the experiment until equilibrium is reached.  (Don’t bother timing this yet.)
2. Person A will call “Stop” when they think equilibrium has been attained and note the data in a table as before.
3. Add Lego in singles to the bench and person A should note this data as well (both data points, this and the previous one,  are at time zero).
4. Person A will call “Start” and run the experiment taking data every 15 seconds as in part 1.
5. Proceed until a new equilibrium point has been reached.
6. Redo the above from 1 but add Lego in doubles.
7. Graph the results on one graph.
8. Discuss in terms of Le Chatelier’s Principle.