Lab 9 Procedure

Welcome to Chemistry Mystery Hour

Today you will need to solve the mystery of an unknown product. By decomposing baking soda (sodium bicarbonate) you must figure out what product you made. Did you make sodium hydroxide, sodium oxide, or sodium carbonate? Using the wonders of STOICHIOMETRY you will be able to solve this mystery! Good luck!

In this lab you will:

  1. Decompose baking soda (sodium bicarbonate)

  2. Perform three stoichiometric calculations to determine your product

  3. Confirm your chosen product by testing with red cabbage juice indicator and hydrochloric acid.

Safety for this lab:

  • Wear safety glasses at all times.

  • Perform all burning and heating in the fume hood.

  • ALWAYS clean up your entire station and any spills made at shared stations.

  • DO NOT deposit broken glassware in trash, place into broken glassware container located near paper towels.

The proper number if significant Figures will be used for all measurement recordings and all calculation answers.

Part 1: Decomposition reaction of baking soda (sodium bicarbonate).

Set up the ring stand with a clay triangle and Bunsen burner in the fume hood.  Making sure the crucible will be extremely close to the flame of the burner when it’s placed on the clay triangle.

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Thoroughly heat your crucible and allow it to cool on the clay triangle. This ensures that it is clean and dry. Using the balance record “mass of crucible with lid”. 

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Place a small scoop of baking soda (sodium bicarbonate) into the empty crucible, about 1/4 filled. Using the balance record “mass of crucible, lid, and NaHCO3“.

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Heat the baking soda in the crucible for at least 15 minutes. While this is heating, it is suggested to work on the calculations of “Theoretical Yields of Possible Products” on Data Sheet. 

For help with calculations: Refer to Pre-Lab 

Continue to break apart any solid clumps that form. Leave the lid slightly off as shown in the picture below.  

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Further Information in regards to the Calculations:

  • This laboratory involves decomposing sodium bicarbonate by heating.
  • There are three very plausible reactions as shown on Data Sheet. 
  • Using the “mass (grams) of NaHCO3” on your Data Sheet, you will perform three stoichiometric calculations to determine which product you made. Possibly: NaOH(s) or Na2O(s) or Na2CO3(s)

Now Determine Your Product (Solve the Mystery)

After heating is complete, allow the crucible to cool. Using the balance record, “mass of crucible, lid, and product”  

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Using a little subtraction on your Data Sheet determine the mass of just your product which we call the “ACTUAL YIELD”. Compare this mass to your stoichiometry calculations:

  • “theoretical mass of NaOH(s)”
  • “theoretical mass of Na2O(s)” 
  • “theoretical mass of Na2CO3(s)”

Your product mass should match one of these and so this is your “Possible product”

Calculate the Percent Yield to see how well you did this experiment.

Percent yield = (actual yield) divide by (theoretical yield) x 100

Mystery Solved! Maybe… Let’s just do some more testing to confirm:

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First Test: Comparison of color change with INDICATOR

Place a few drops of sodium hydroxide (NaOH) solution into a 1st test tube.

Place a few drops of sodium carbonate (Na2CO3) solution into a 2nd test tube.

Place a small amount (HALF) of your product into a 3rd test tube.


Now add the red cabbage juice indicator to each test tube and you should initially see all samples look green. Wait about 30 seconds to a minute until one sample turns yellow. Now compare the color of your product to the color of the NaOH solution and the Na2CO3 solution, it should match one of them.


Note: One possible product is sodium oxide but when sodium oxide dissolves in water it produces sodium hydroxide.

Second Test: Comparison of product with HYDROCHLORIC ACID (HCl)

Place the remaining amount of your solid product (the stuff left inside the crucible) into a small test tube.

Using a disposable pipet, add a few drops of HCl solution to your product.


  • If your product is sodium carbonate, the HCl will react and you will observe bubbling as a result of a gas being released.

  • If your product is sodium oxide, the HCl will dissolve quietly and you will observe no visible change.

Hopefully you correctly solved this Chemistry Mystery! Good Job!

FINAL STEP: CLEAN YOUR STATION 

Use the sinks and soap to wash your glassware. 

PUT AWAY ALL EQUIPMENT AND CHEMICALS AND WIPE DOWN YOUR STATION.

Do not leave the lab until the instructor has inspected your clean station.

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