Name:_____________________________ Period:______
Law of Conservation of Mass Lab
Purpose: To attempt to verify & observe the Law of Conservation of Mass - In any chemical reaction, the total
mass of the reactants is always equal to the mass of the products.
Materials:
 Balance
 1 balloon
 weighing paper
 50 mL flask



50 mL graduated cylinder
5 g baking soda
15 mL vinegar
Introduction: The word equation for the following reaction is as follows:
vinegar + baking soda →
sodium acetate + water + carbon dioxide
The chemical equation for the reaction is:
CH3COOH + NaHCO3 →
Reactants
NaC2H3O2 + H2O + CO2
Products
Procedure:
1. Record the mass of the empty flask.
2. Record the mass of the empty balloon.
3. Record the mass of the graduated cylinder. Measure 15 mL of vinegar using the graduated cylinder.
Record the mass of the graduated cylinder with the vinegar in it. Subtract the two measurements to
get the mass of the vinegar only….. record.
4. Pour the 15 mL of vinegar into the flask.
5. Measure 5 g of baking soda on the weighing paper. Put the 5 g of baking soda into the balloon.
Weigh the balloon with the baking soda in it. Check to see if the two masses added together equal what
you actually measured.
6. While one student holds the flask, another must slip the open end of the balloon over the mouth of the
flask, while keeping the baking soda from entering the flask.
7. Weigh the whole system and record the mass. (See the Picture!!!)
8. Tip the balloon upright, allowing the baking soda to drop into the flask and allow the reaction to fully
complete.
9. After the reaction is completed, find the mass of the balloon, flask, baking soda and vinegar
(Do not let any gas escape from you’re the system that you set up) (See the picture)
10. Return the empty balloon to me and rinse everything down the drain.
Step 7
Step 9
Data:
Material
Flask
Mass (g)
Total mass of all objects after the reaction occurred
Balloon
-------------------------------------- grams
Vinegar (15 mL)
Baking soda
Compare the mass of your all your objects before the
reaction and after the reaction. Are they the same?
Total mass of all objects
(add the above together):
________________
Total mass that the scale
reads:
________________
Analysis Questions:
1. Was your mathematically calculated total mass of the system the same as the measured mass of the
system? ___________If not, then can you explain why?
2.
What evidence was there to indicate that a chemical reaction occurred?
3. How did the final (products) mass of the system compare with the initial (reactants) mass of the system
for each trial? How did your result support or violated the Law of Conservation of Mass?
4. List the reactant chemicals and indicate its state of matter.
5. List the product chemicals and indicate its state of matter.
6. How else could you have tested the law of conservation of matter for this reaction? What other
experimental designs could you have implemented? Write a different procedure that can be used to test
this law. Use a separate sheet of paper and attached it behind this one.