Effectiveness of Antacid Tablets
Purpose: The purpose of this experiment is to compare and
measure the effectiveness of antacid tablets using an acid titration.
Introduction: Different brands of antacids contain a diverse range
of active ingredients but all have the purpose of neutralizing excess stomach
acid (HCl) by acting as a base. A chemical technique called a ‘titration’ can
be used to see how much acid an antacid tablet can neutralize. When a base is
added to an acid, water and salt are formed. This is called neutralization.
When a known amount of acid is added to an unknown amount of base, a measurable
amount of the acid is neutralized. By measuring the amount of acid neutralized,
the initial amount of base can be determined. The stronger the antacid, the
more acid can be neutralized. For example, Tums uses the base calcium carbonate
(CaCO3) as the active ingredient. For each molecule of calcium carbonate, two
molecules of acid are neutralized. The reaction occurs in two steps:
CaCO3 + HCl à (CaCl)+ + HCO3-
+ HCl ßà CaCl2 + H2CO3
The second step of the
reaction is reversible, making bicarbonate and carbonic acid, respectively,
which is the main buffering system in the human body. The salt formed here is calcium(II) chloride. The titration done in this experiment
uses the chemical indicator methyl orange, which changes color from yellow to
red at a pH of 3.1-4.4. The antacid is considered ineffective at a pH of 3.
Available Supplies
Beakers, HCl (acid), biuret,
antacid tablets, mortar & pestle, 50 mL of water
Procedure
1.
Are there any
factors we need to control?
2.
Can you leave the
tablet solid or does it need to be altered in some way?
3.
How do you know
when you are done?
4.
How will we
determine the amount of acid a tablet of antacid can neutralize?
Follow-up Questions:
1.
What antacid was
most effective in neutralizing stomach acid?
2.
What is the
active ingredient in this antacid?
3.
Are the results
for this antacid consistent with other antacids tested that have
the same active ingredient? Explain your reasoning
4.
Using the
internet, evaluate the pros and cons of different ingredients. Discuss which
act faster, longer and which have fewer side effects.
5.
Why do we stop
the titration when the solution reaches a pH of about 3?
Data:
Type of Antacid
______________
Amount of active
ingredient____________
Mass of tablet 1________________ Mass of tablet 2___________
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pH |
Amount of Acid Added |
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pH |
Amount of Acid Added |
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Once you have collected your
data put your final pH and total amount of acid on the board (your instructor
will put up a table). Then you will enter all of the class data into SPSS for
use in statistical analysis.