Equilibrium

Introduction

In a terrarium, the liquid water and its vapor are in equilibrium. If the terrarium gets colder some of the water vapor will condense, then there will be more liquid water than vapor water in the new system. Based on Le Châtelier’s Principle, changes in temperature, pressure, concentration of reactants or products are ‘stresses’ that could affect a system’s equilibrium.

Materials

Procedures

  1. Separate marbles by colors. You should have 30 blues, 30 oranges, 30 greens, and 50 yellows.
  2. Mix 30 blue marbles into the cup that has the 30 orange marbles. Use the other cup as the cap when you shake/‘react’ your marbles.
  3. Do NOT spill or crack your ‘chemicals’, a.k.a. marbles.
  4. Record the starting numbers and concentrations for reactants and products in your data table as trial 0.
  5. Allow the marbles to react by shaking the cup. (This represents a collision between these marbles, possibly leading to a chemical reaction.)
  6. Pick out 3 marbles.
  7. After each reaction, determine the number and the concentration (percentage) of blue, orange, green, and yellow marbles that remain in the cup.
  8. Determine whether a forward or reverse reaction just occurred.
  9. B + O ↔ G + 2Y
  10. Continue to allow the marbles to react until you have reached equilibrium.

Data

Reaction # # B # O # G # Y Total # forward/reverse [B] [O] [G] [Y]
0 30 30 0 0 60 N/A 0.50 0.50 0.0 0.0
1 ??? ??? ??? ??? ??? ??? ??? ??? ??? ???
2 ??? ??? ??? ??? ??? ??? ??? ??? ??? ???
etc... ??? ??? ??? ??? ??? ??? ??? ??? ??? ???

Analysis

1. How do you know if equilibrium has been reached? ???
2. Does Keq agree with your deduction?
3. What did you notice about the OVERALL speed or the rate of the reaction as you neared equilibrium? Explain on the molecular level. ???
4. Were products or reactants favored in this reaction? ???
5. If this were an exothermic reaction, do you think the products or reactants would be favored? ???
6. What conditions you could change to produce more blue marbles? ???



How to do this assignment?

Chemistry in March