A Quick and Dirty Stoichiometry Lab...Differentiation and Inquiry?

Quick Stoichiometry Lab

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How do I know when they are there?

What is the evidence?

There is a traditional stoichiometry lab I have done before that involves adding dilute hydrochloric acid to sodium bicarbonate, boiling off the fluid and then getting the mass of the sodium chloride. Students then can solve the percent yield for the sodium chloride based on the amount of sodium bicarbonate they use. It is not a bad lab, but having hot ceramic watch glasses with acid in them just makes me a bit nervous. I am not sure where I got this new lab I am about to share, but it has been one that has evolved over the years. It is quick, dirty, relatively simple and uses over the counter (mostly) materials, making it much safer than the traditional lab that I used to assign.


First we start with some over the counter effervescent cold tablets. The brand name is "Alka Seltzer". Students are asked, "How can you figure out the ingredient that makes the bubbles?" Students brainstorm questions which are all collected and recorded. Next, we start in on stoichiometry. Ultimately, students figure out that they need the balanced equations to solve this problem. The nice part about this lab is that there are many substances in these tablets, however, the bubbles seem to only come from the baking soda. Students are provided the question and as a class we work on safety, procedure, materials and data. It is eventually decided that students will use dilute hydrochloric acid to react a portion of the tablet. After the bubbles stop, they let the test tube sit in a bit of warm water for a few minutes to help drive off all of the carbon dioxide. It is important to slowly add bits of the tablet to the acid. students record the mass of the tablet and materials before the reaction and they record the mass of everything after. The only difference is that after the reaction, the total mass is less due to the escaping carbon dioxide. The mass of the carbon dioxide can be converted to moles. From here, students use the balanced equation to solve for moles of sodium bicarbonate and then grams. Students then are given the mass of an entire tablet and to solve for the sodium bicarbonate in a whole tablet. They are also provide with the amount of sodium bicarbonate the manufacture claims is in the tablet.


This lab can be used many different ways. A teacher can stress the inquiry part, designing an experiment, experimental versus theoretical results, dimensional analysis, stoichiometry, significant figures or balancing reactions. Depending on your class, you can pick which aspects you believe would be appropriate for your students. About ten to fifteen minutes are required to complete the procedure and collect data. Sometimes, students add too much of the tablet all at once and the test tube over flows. It is simple and easy enough to start over. Overall, it seems to be a relatively simple lab that can pack an educational punch on several levels. The nice part is that you can adapt the lab to best meet the needs of your students. In other words, it is a form of differentiation.


Ultimately, it is about our students. It is tough and exhausting. The other day, I saw a great sign. It was a drawing with a circle that said "Comfort Zone" inside the circle. Outside the circle was a dot with an arrow and the phrase said, "This is where learning begins." Let's have fun as we take on the journey to learn along with our students.......


Editor's Note - Responding to a request for a student handout, Chad submitted what he provides for students. You will find it in the Supporting Information below if you are logged in to your ChemEd X account.. 2/22/18




General Safety

For Laboratory Work: Please refer to the ACS Guidelines for Chemical Laboratory Safety in Secondary Schools (2016).  

For Demonstrations: Please refer to the ACS Division of Chemical Education Safety Guidelines for Chemical Demonstrations.

Other Safety resources

RAMP: Recognize hazards; Assess the risks of hazards; Minimize the risks of hazards; Prepare for emergencies



Students who demonstrate understanding can use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

*More information about all DCI for HS-PS1 can be found at https://www.nextgenscience.org/dci-arrangement/hs-ps1-matter-and-its-interactions and further resources at https://www.nextgenscience.org.


Students who demonstrate understanding can use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

Assessment Boundary:

Assessment does not include complex chemical reactions.


Emphasis is on using mathematical ideas to communicate the proportional relationships between masses of atoms in the reactants and the products, and the translation of these relationships to the macroscopic scale using the mole as the conversion from the atomic to the macroscopic scale. Emphasis is on assessing students’ use of mathematical thinking and not on memorization and rote application of problem - solving techniques.

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Comments 12

Marcy Clark | Wed, 02/21/2018 - 08:21

I really like this idea of using something that they may come in contact with in everyday lives.  Do you have a handout made or teacher notes made that you wouldn't mind sharing?

Deanna Cullen's picture
Deanna Cullen | Thu, 02/22/2018 - 19:05

Hi Marcy! Thank you for your interest in ChemEd X. I am glad you have found Chad's post helpful. I have attached the student handout that Chad sent me in response to your request to the Supporting Information.  



Dawn Mortimer | Wed, 01/08/2020 - 14:47

This is our first year teaching Chemistry to every student.  I used this idea to adapt a version I believe will help all of my students attain a deeper understanding of the very abstract subject of Stoichiometry!  Thank you!

Chad Husting's picture
Chad Husting | Thu, 01/09/2020 - 19:34

Dawn, I am glad I could help.  If you come across any other activities that seem to work well, please share!

Thanks again.

Donna Engel | Fri, 01/10/2020 - 09:10

What molarity of HCl do you use?  Would vinegar also work?

Kyla Gurganus's picture
Kyla Gurganus | Sun, 05/14/2023 - 19:16

My colleague and I used the Alka-Seltzer + hydrochloric acid lab this past week as an application of stoichiometry with good results.  Thank you for posting!

Chad Husting's picture
Chad Husting | Mon, 05/15/2023 - 13:34

Glad you liked the lab.  FYI...I use 1 to 1.5 M HCl.  Make sure it is in excess.  I have never used vinegar before.  Vinegar is typically around 3% by mass for normal vinegar and about 6% by mass for cleaning vinegar.  In theory it should work but I would try it first and again, do a quick calculation to make sure the vinegar is in excess.  Hope this helps.

Susan Schmidt's picture
Susan Schmidt | Tue, 05/16/2023 - 07:33

This would be a great intro lab to the traditional salt from soda lab - it's great that you can use the mass lost to find the mass of sodium bicarbonate.

We do a lab using two unknown powders - one is sodium bicarbonate (baking soda) and the other is sodium carbonate (washing soda). The students then react a known mass of their unknown powder with HCl until it completely reacts, then boil off the water to get only sodium chloride. By doing stoich calculations with both types of soda, they can figure out whether they were given a sample of sodium bicarbonate or sodium carbonate, based on the mass of salt they produce.

Chad Husting's picture
Chad Husting | Thu, 05/18/2023 - 12:41

Great Idea!  I love anything that can be easily turned into a guided inquiry lab and student's cannot easily find the answer online.  Awesome! I would love to try this!  Thank you!

Chad Husting's picture
Chad Husting | Sun, 05/21/2023 - 11:21


Thanks for sharing.  I absolutely love the lab.  It uses a popular product students will use and it covers multiple concepts.  I really get excited when I see something that can be used in more than one way or as a tool to reinforce concepts that we have already covered.  We typically cover acids and bases at the end of the year.  This would not only cover acid bases but also key parts to stoichiometry.  You should write for ChemEdX!  Thanks so much for sharing!

Lynn Skutches's picture
Lynn Skutches | Sun, 05/21/2023 - 15:11

Thank you so much for your kind words, Chad.  So glad you think it is helpful. I appreciate your confidence in my abilities, and hope I can share a small bit of what has been so generously shared with me in the coming year :)