How Big is the Balloon?
Summary
In this Chemistry lab, students will investigate limiting reagents and balanced chemical equations. A simple experiment that should give students a physical example of what "limiting reactant" means.
CollapseLearning Goals
This activity is designed for students to use an Inquiry based activity to comprehend the concept of limiting reagents. The inquiry develops stoichiometry and writing balanced reactions.
Key Words:
stoichiometry, limiting reagents, chemical equations
Key Words:
stoichiometry, limiting reagents, chemical equations
Context for Use
The activity can be completed in a general chemistry lab. The lab should be completed in one block or 1 1/2 class periods.
The concept of stoichiometry and writing balanced reactions must have been introduced prior to the lab; however, it is a nice activity to introduce the idea of limiting reagents.
The concept of stoichiometry and writing balanced reactions must have been introduced prior to the lab; however, it is a nice activity to introduce the idea of limiting reagents.
Description and Teaching Materials
How big is the balloon?
Purpose:
Can you change the amount of products by changing the amount of only one reactant?
FYI
This mini-lab uses the common reaction between baking soda (NaHCO3) and vinegar (~1.0 Molar acetic acid: C2H3O2H) to produce sodium acetate and carbon dioxide.
Safety
Standard precautions. Also: Be especially careful of materials being splashed or sprayed - protect your eyes!
Procedure:
Use exactly 5.0 grams of baking soda in each balloon that you test. Only vary the amount of vinegar. Technique: put baking soda into a balloon. Put vinegar in a test tube. Stretch the balloon over the top of the test tube and pour the vinegar into the balloon. Put the test tube, with the balloon on it, into a rack and observe.
Purpose:
Can you change the amount of products by changing the amount of only one reactant?
FYI
This mini-lab uses the common reaction between baking soda (NaHCO3) and vinegar (~1.0 Molar acetic acid: C2H3O2H) to produce sodium acetate and carbon dioxide.
Safety
Standard precautions. Also: Be especially careful of materials being splashed or sprayed - protect your eyes!
Procedure:
Use exactly 5.0 grams of baking soda in each balloon that you test. Only vary the amount of vinegar. Technique: put baking soda into a balloon. Put vinegar in a test tube. Stretch the balloon over the top of the test tube and pour the vinegar into the balloon. Put the test tube, with the balloon on it, into a rack and observe.
Teaching Notes and Tips
The lab gives a simple experiment that should give students a physical example of what "limiting reactant" means.
Discussion ideas: Talk with them about the idea of limiting reactants. You might set up a contest and test their guesses for question #6. What assumptions are made in answering question #5 (balloons are the same volume, degree of elasticity, etc.)?
Discussion ideas: Talk with them about the idea of limiting reactants. You might set up a contest and test their guesses for question #6. What assumptions are made in answering question #5 (balloons are the same volume, degree of elasticity, etc.)?
Assessment
Lab Questions
FINAL: Is there a way to calculate the exact point at which the combination of baking soda and vinegar has reached maximum production of carbon dioxide? If so, show how you would do it.
- Write a balanced chemical equation for this reaction.
- How much vinegar is required to maximize the production of carbon dioxide?
- If you added more than this amount of vinegar, would you make any additional product? Why or why not?
- How many moles of carbon dioxide are in the balloon at the point of maximum production? How can you figure that out?
- Does the amount of vinegar change the time that it takes to complete the reaction?
- Is it possible to cause the balloon to burst using only 5.0 grams of baking soda? If not, what is the MINIMUM amount of baking soda (and vinegar) that would burst the balloon (based on your observations)?
FINAL: Is there a way to calculate the exact point at which the combination of baking soda and vinegar has reached maximum production of carbon dioxide? If so, show how you would do it.
Standards
IIB1, IIB2, IIB4