Limiting Reactant Lab: The reaction between vinegar and baking soda.
Goal: During this lab students will gain a quantitative understanding of limiting reagents.
Objective: Obtain experimental data and use it to determine the limiting reactant in a chemical reaction.
SC.912.P.8.9: Use experimental data to determine limiting reactant and calculate the mass-to-mass stoichiometry for a chemical reaction.
MAFS.912.N-Q.1.3: Choose a level of accuracy appropriate to limitations on measurement when reporting quantities.
LAFS.910.SL.2.4: Present information, findings, and supporting evidence clearly, concisely, and logically such that listeners can follow the line of reasoning and the organization, development, substance, and style are appropriate to purpose, audience, and task.
Safety: Safety goggles should always be worn.
Students should hold the balloons on the test tubes tightly while the reaction takes
1) Using the graduated cylinder accurately measure and transfer 10.0 mL vinegar (5% acetic acid, HC2H3O2) into each of the 6 test tubes.
2) Weigh the following six amounts of baking soda (sodium bicarbonate, NaHCO3): 0.20 g, 0.40 g, 0.50 g, 0.70 g, 1.00 g, and 1.70 g (use a weighing paper to do it).
3) Label the balloons 1-6. Put the six different masses of baking soda into six balloons using a small funnel. Make sure the baking soda goes to the bottom of the balloon.
4) Attach the filled balloons to the mouth of the test tubes. Make sure that the contents of the balloon and test tube are not mixed.
5) Before mixing the contests of the balloons and test tubes, make a prediction about which combination will produce the greatest amount of carbon dioxide gas (hypothesis).
6) After the balloons are securely attached to the test tubes, each group member needs to lift a balloon on one of the test tubes so that the content of the balloon mix with the test tube content. All six test tubes should be reacted simultaneously.
When the reactions are done, record your results in the table provided.
Evidences of Chemical changes: _______________________________________
Rank the balloons from the smallest to the largest.
|smallest |next |next |next |next |largest | |Balloon’s Number | | | | | | | |
# |Mass of NaHCO3
(g) |Moles of NaHCO3 |Volume of acid, (mL). |Moles of acetic acid. |Experimental mole ratio:
NaHCO3/ acetic acid. |Reactant in exceso. |Limiting reactant. |Moles of CO2 obtained. | |1 |0.20 g | |10.0 | | | | | | |2 |0.40 g | |10.0 | | | | | | |3 |0.50 g | |10.0 | | | | | | |4 |0.70 g | |10.0 | | | | | | |5 |1.00 g | |10.0 | | | | | | |6 |1.70 g | |10.0 | | | | | | |
Experimental mole ratio ˃ Theoretical mole ratio --- The Limiting reactant is the substance used in the denominator of the fraction & vice versa.
Results and analysis (Post Lab): (You must show all your work in your report).
1) Rank the test tubes in order of the least to the greatest amount of carbon dioxide gas (CO2) produced.
2) Write the balance molecular equation for the reaction that took place.
3) What is the identity of the gas that inflated the balloons?
4) What is the theoretical mole ratio of sodium bicarbonate to acetic acid for the reaction? Show your work.
5) Find the number of moles of baking soda used in each reaction (NaHCO3 = 84.0 g/mol). Show your work. Write your finding on the table.
6) Determine the experimental mole ratio of sodium bicarbonate to acetic acid for each reaction (there are 8.3 x 10-3 moles of acetic acid in 10.0 mL of it). Show your work. Fill out the table.
7) Comparing theoretical & experimental mole ratios and identify the chemical that was in excess and the limiting reactant in each test tube. Fill out the table.
8) Calculate the number of moles of CO2 formed in each test tube. Show your work. Complete the table.
9) Are your results agreed with your prediction? Explain.
10) List the possible errors.
What happens if you make a cake without baking soda? If you don't have this ingredient at hand, use a baking soda substitute. Without it, your cake won't rise and can turn out flat. Leaving baking soda out of the cake prevents it from rising, but you can use baking powder as a substitute.