Acids & Antacid Lab
Prelab Questions:
1. What are the main ingredients for each of the
antacids?
2. What is the dose (in grams) for each tablet?
3. Which antacid do you think is going to be the best
neutralizer?
4. What is the amount of antacid to be used in lab?
5. What is the amount of acid to be used in lab?
6. What is the molar mass for each antacid and acid
used?
Show work!
I. Introduction
All antacids serve to relieve acid indigestion with varied
degree of effectiveness, by neutralizing the excess
hydrogen ions (H+ or hydronium) in the stomach. Antacids
are basic pH with one or more neautralizing compounds. To
decrease the possibility of the stomach becoming too basic
from the antacid, buffers are added as part of the
formulation of some antacids. In this experiment, the
neutralizing powers of several antacids are determined
using a strong acid-strong base titration. So in the lab,
students will be neutralizing “stomach acid”
or hydrochloric acid with three antacids to determine
which one is the best.
II. Procedure
1. Measure roughly 1 g of all antacid tablets (Alka
Seltzer, Tums & Rolaids). Transfer to a small flask.
Calculate molecular (molar) mass of each antacid. This is
done by adding up all the atomic weights of the elements in
the compound.
For example: CaCO3 (grams) = Ca(40g/mol), C(12g/mol),
O(16g/mol)x3 = 100g/mol
2. Pipet 30 mL of soda (substituted for 0.01 M HCl) into a
seperate flask and swirl to dissolve. Add 10 drops of
bromothymol blue indicator . If the solution is blue, pipet
an additional 30 mL of 0.1 M HCl into the solution. The
solution should turn yellow. Repeat as often as necessary.
Record the total volume of HCl added.
3. Obtain 25 ml of distilled water in a graduated cylinder
and add the first antacid to it. This will create a 0.5 M
solution for the Tums, but it will be different for the
other antacids. Prepare a buret and a stand for titration
and fill it with the antacid solution.
4. Once the antacid solution is ready, carefully titrate
the acid sample with the antacid solution to a blue
endpoint. When a single drop of antacid solution changes
the sample from yellow to blue, stop. Wait for 30 seconds
and then read the final volume of antacid solution in the
buret (in mL) and record it.
5. Repeat the titration of the same sample and for the
other antacids.
III. Post Lab Questions/ Analysis & Calculations
1. Calculate how much of EACH antacid was needed to
neutralize the solution.
(mass base in antacid/ mol of antacid) (g/mol)
2. Calculate how many moles of EACH antacid there was
needed to neautralize the acid. (This is how you will
determine which antacid is better).
HINT The # of moles of base in the antacids used in the
titration = # of moles of HCl.
3. Which of the three antacids was most effective gram for
gram? Why?
4. Why is water the best molecule for these experiments?
5. Did each of the experiments work? Which was the best
representative for each acid absorbing material & WHY?
(Defend your answer.)
6. What did the data collected tell you about each
experiment?
Conclusion Questions
7. Did the lab make any major scientific discoveries or
breakthroughs? Was the lab group scientific?
8. Were there any other antacid experiments that could be
done in lab to illustrate neutralization?
9. What changes could be made to make the lab better?
10. What were the favorite or least favorite experiments?
WHY?