Limiting Reactant

Balloons filled with different amounts of baking soda are attached to flasks containing vinegar, producing varying amounts of carbon dioxide gas.

1. Fill five Erlenmeyer flasks with 70 mL of vinegar each.
2. Measure out 2 g, 4 g, 6 g, 8 g, and 10 g of baking soda into separate balloons.
3. Carefully attach each balloon to a flask so that the baking soda does not spill into the vinegar.
4. Raise the balloons one at a time to drop the baking soda into the vinegar.
5. Observe the size of the balloon inflation and whether any solid remains at the bottom of the flask.
6. Add bromothymol blue to each flask after the reaction:
   1. Yellow solution = vinegar in excess (acidic).
   2. Blue solution = baking soda in excess (basic).
   3. Green solution = near neutral, close to stoichiometric balance.
7. Confirm predictions by adding extra vinegar to the basic flask and extra baking soda to the acidic flask.
8. Guide students to calculate the limiting reagent, the excess reagent, and the amounts of products for each flask.

Chemical Reactions: Limiting Reagents - Science World:

Limiting Reactant Demonstration - cheminstrinaminute:

📄 Limiting and excess reagents - University of Waterloo: https://uwaterloo.ca/chem13-news-magazine/december-2015-january-2016/activities/sharing-chemistry-community-limiting-and-excess-reagents

• Use a gas syringe to measure the volume of carbon dioxide more precisely instead of balloon size.

• Wear safety goggles and gloves when handling vinegar and indicator.
• Avoid ingestion, inhalation, or skin contact with bromothymol blue.

• How does the size of the balloon indicate which reagent is limiting?
• Why does leftover baking soda or vinegar signal the presence of an excess reagent?
• What do the color changes with bromothymol blue reveal about the solution?
• How do stoichiometric calculations confirm the experimental results?