How can I test the quality of a tums (antiacid) tablet through a titration?

Question

Our chemistry professor has asked us to design our own lab experiment and we wanted to do a titration, he suggested that we test the quality of an antiacid tablet. We’ve accepted, but have a small idea on what to do bring the average students that we are.

Answer 1

Look up the active ingredients in the antacid tablet that you are using. It will probably be something like calcium carbonate (CaCO₃) or magnesium hydroxide (Mg(OH)₂). Whatever it is, it will be a base so that it can neutralize the stomach acid (HCl).

Once you have the active ingredient, write the balanced equation for the reaction with HCl. For example, if you use Tums, you will have CaCO₃ + 2HCl ==> CaCl₂ + H₂CO₃ and the H₂CO₃ ==> CO₂ + H₂O.

You can test the "quality" of the tablet by weighing the tablet, dissolving in water (whatever will dissolve) and titrating this solution with a known concentration of HCl. Determine how many moles of HCl it takes to neutralize the pre-measured mass of tablet. From the balanced equation above, you can calculate moles CaCO₃ and then grams of CaCO₃ and compare that to grams of tablet originally weighed. Of course the calculated value will be less because the entire tablet isn't CaCO₃ but contains other ingredients as well. You can compare and see what percent of the tablet is actually CaCO₃.