LIMITING REACTANT LAB
PURPOSE: To determine the limiting reactant for a specific reaction in which amounts of reactants are carefully measured.
PRE-LAB DEFINITIONS: Limiting vs. Excess Reactant
MATERIALS & PROCEDURE:
1. Using a ring stand, clamp and wire gauze, make a hot water bath by filling a 400-600 ml beaker about 2/3-3/4 full with tap water. Heat the beaker to a boil.
2*. Add 0.50 grams of Copper (II) Sulfate to a test tube.
3**. Add 15 ml of distilled water to the test tube and shake to mix the solution. NOTE THE COLOR OF THE SOLUTION.
4*. Obtain piece of aluminum foil which has an area of approximately 50 square cm. Record the mass of the foil.
5. Lightly wrap the foil around a pencil. Put the foil tube into the test tube with your solution.
6. Place the test tube in the hot water bath. Don’t dump the contents of the tube into the beaker. Just place the tube upright in the beaker. Once boiling, continue heating the test tube for approximately10 minutes.
7**. Note the final color of the solution (Should be different. If not, continue heating). Carefully remove the foil from the tube and record observations about the foil’s appearance.
8. Carefully, rinse all particles off of the remaining foil with H2O.
9*. Dry the foil carefully and completely with a paper towel and record its mass.
10. Clean all glassware and put everything back where it belongs.
DATA & OBSERVATIONS: Make a data table and record important measurements & observations. (in procedure “*” denotes quantitative data, and “**” denotes observations)
CALCULATIONS AND QUESTIONS (Use Complete Sentences):
1. What happened to the color of the solution as the reaction proceeded? From a chemical perspective, why did this happen?
2. What does the aluminum look like at the end of the lab (look closely)?
3. Based on your observations during the lab, identify the limiting reactant and the excess reactant. Explain your answer.
4. Write the balanced equation for the reaction which took place. What is the identity of the brown solid which formed?
5. Using the amounts of aluminum and copper (II) sulfate you reacted together, use stoichiometry to determine how much copper should have formed in this reaction. This will require two stoichiometry calculations.
6. Based on your calculations in #6 what was the limiting and excess reactant? Explain how you know.
7. Using your data, calculate the mass of aluminum which actually reacted. This is simply a subtraction problem using your data.
8. Using stoichiometry, determine how many grams of the aluminum should have reacted. Take note of how closely this answer matches #7.
9. Calculate your percent error for your process. The experimental value is your answer to #7. The accepted value is your answer from #8.
QUESTION:
Here is a limiting reactant problem: Now you react 2.00 grams of Aluminum with 8.9x10-2 grams of oxygen gas. How many grams of aluminum oxide will form?
CONCLUSION:
Write a conclusion which demonstrates that you understand what you did. How did you accomplish the purpose? Discuss the math as well.
Remember, here is a great guide for writing your conclusion:
1) Restate the purpose
2) Summarize the procedure
3) Explain the math
4) Report your results
Also, please include any other interesting information you would like to add.