Baking Soda Stoichiometry

Introduction: When baking soda is an ingredient in a bisquit recipe, its purpose is to make the batter rise and produce biscuits with a light and fluffy texture - there is nothing worse than a rock hard and flat biscuit (that's called hard tack!).  The baking soda (chemical name is sodium hydrogen carbonate or sodium bicarbonate) decomposes upon heating to produce sodium carbonate and carbon dioxide and water.

In this lab, you will predict how much (in grams) of sodium carbonate is produced when baking soda decomposes.  Then, you perform the process of decomposition and actually determine the mass of sodium carbonate that was actually produced.  You will then calculate your % error.

Materials:

• crucible with lid
• ring stand and wire mesh
• crucible tongs
• bunsen burner
• analytical balance
• baking soda (sodium bicarbonate)

Procedure:

1. NOTE: Do NOT take your calculators into the lab.  You will do all calculations and analysis on your own and outside of the lab!
2. Laboratory Data Table and Analysis Questions - Print off here if needed.
3. On your data table, balance the equation you will be working with in this lab. 
4. Get a crucible and lid.  Make sure it is clean and completely dry.  Using the analytical balance, measure the mass and write it onto your data table.
5. NOTE: Be sure to always use the SAME analytical balance for your weighings.
6. Add about a half teaspoon of baking soda.  Using the analytical balance, measure the exact mass of the crucible, lid and baking soda.
7. On your data table, determine the actual mass of just the baking soda.  Then, perform the stoichiometry and determine the amount of sodium carbonate that should be produced from the decomposition.  Write that amount into your data table.
8. Set up a ring stand, wire mesh and bunsen burner. 
9. SLOWLY heat the crucible with the lid closed on the crucible.  Then, after about 5 minutes, begin a "harder" heat - SLIGHTLY cock the crucible lid to allow the water and carbon dioxide to escape.  This second phase of the heating should be for about 10 minutes. 
10. Allow the crucible to cool.
11. Using the analytical balance, record the final mass of the crucible, lid and final product on your data table.
12. Dispose of the crucible contents in the trash.  Thoroughly clean out and dry your crucible and lid.  Return to the front lab table.
13. CLEANUP: Take a wet paper towel and thoroughly swab down your lab table.  Then, take a dry paper towel and thoroughly clean out the middle sink area of your lab table. 

Analysis:

These questions are incorporated on your laboratory sheet:

1. What was your starting actual mass of the sodium bicarbonate?
2. What was your expected (theoretical value) of the sodium carbonate you should have gotten?
3. What was your final actual mass of the sodium carbonate?
4. What was your percent error for this experiment?
5. If you had more than 5% error, if you were to repeat this lab, what would you do differently next time in order to minimize error?