The document describes an experiment testing the effectiveness of various antacid tablets at neutralizing stomach acid. Antacids work by chemically reacting with hydrochloric acid in the stomach through neutralization reactions. The experiment measures the number of drops of hydrochloric acid needed to reach a pH of 2 when added to solutions of different crushed antacid tablets. This determines which antacid requires the most acid to become neutralized, indicating it is most effective at relieving excess stomach acid. Safety precautions for the experiment and procedures for preparing, titrating and recording results for each antacid are provided. The purpose is to compare the acid-neutralizing abilities of common antacids to determine the most

1. Testing
Antacids
Abinaya Helbig
PERFORMED
03/11/2010
SUBMITTED
03/24/2010
SNC2D0-G
BACKGROUND Mr. Shaughnessy, J.
INFORMATION /
PRE-LAB
INFORMATION

2. [TESTING ANTACIDS] March 11, 2010
The stomach contains a solution of hydrochloric acid called gastric juice, which has a normal pH
of about 1.5. Gastric juice is important for digestion, but it may irritate the stomach lining and cause
tenderness if the acid is too intense/ concentrated. This can result in symptoms of heartburn and
contribute to stomach ulcer. However all this can be prevented by consuming antacid tablets.
What are Antacids?
Antacids are substances that consist of weak bases (commonly hydroxide, and carbonate).These
substances are used to neutralize overdose of stomach acid and thus ease symptoms of heart burn. There
are several types of commercial antacids which prevent heart burn and stomach ulcers depending on
their effectiveness.
Neutralization
Antacids react with excess stomach acid by neutralization. It is a chemical reaction, (also called
a water forming reaction since a water molecule is formed during the process) in which an acid and a
base or alkali (soluble base) react to produce salt and water (H2O).
i.e. HCl + NaOH → H2O + NaCl
During the process, hydrogen ions H+ from the acid and hydroxide ions OH− or oxide ions O2 −
from the base react together to form a water molecule H2O. In the process, a salt is also formed when
the anion from acid and the cation from base react together. Neutralization reactions are generally
classified as exothermic since heat is released into the surroundings.
Acids are generally pure substances which contain hydrogen ions (H+) or cause them to be
produced in solutions. Hydrochloric acid (HCl) and sulfuric acid (H2SO4) are common examples. In
water, these break apart into ions:
HCl → H(aq) + Cl(aq) OR H2SO4 → H+(aq) + HSO4(aq)
Bases are generally substances which contain hydroxide ion (OH-) or produce it in solution.
Alkalis are the soluble bases, i.e. a base which contains a metal from column 1 or 2 of the periodic table.
To produce hydroxide ions in water, the alkali breaks apart into ions as below:
NaOH → Na(aq) + OH(aq)
Examples of bases include sodium hydroxide (NaOH), potassium hydroxide (KOH), magnesium
hydroxide (Mg(OH)2), and calcium hydroxide (Ca(OH)2). In this project, antacids are bases.
Table 1. Antacids Used In This Lab &Chemical Reactions Involved
Helbig 2

3. [TESTING ANTACIDS] March 11, 2010
Antacid Base Name Formula Balanced Chemical Reaction
Baking Sodium bicarbonate NaHCO3 2HCl(aq) + 2NaHCO3(aq)→2CO2(g) + 2H2O(l) + 2NaCl(aq)
Soda
Rolaids Calcium carbonate CaCO3 2HCl(aq) + CaCO3(aq)→CO2(g) +H2O(l) + CaCl2(aq)
+ + +
Magnesium hydroxide Mg(OH)2 2HCl(aq) + Mg(OH)2(aq)→2H2O(l) + MgCl2(aq)
Eno Sodium Citrate Na3C6H5O7 3HCl(aq) + Na3C6H5O7(aq)→HC6H5O7 + H2O(l) + 3NaCl(aq)
Gaviscon Magnesium carbonate MgCO3 2HCl(aq) + MgCO3(aq)→CO2(g) + H2O(l) + MgCl2(aq)
Tums Calcium carbonate CaCO3 2HCl(aq) + CaCO3(aq)→CO2(g) + H2O(l) + CaCl2(aq)
*Note: Rolaids has two different bases (Calcium carbonate + Magnesium hydroxide).
PURPOSE / PROBLEM
Purpose
The main purpose of this investigation is to test different types of commercial antacid tablets -
mild base that can neutralize acid - for their effectiveness in neutralizing stomach acids, to see if all
antacids are equally effective. Another purpose of this investigation is to learn the way of comparing
antacid tablets in their acid- neutralizing ability to baking soda. Finally another purpose of this
investigation is to determine the amount of acid neutralized by each type of antacid tablet. In other
words, which tablet is the best; as to which one takes the most drops of acid to obtain the pH of 2.
HYPOTHESIS / PREDICTION
Hypothesis
Commercial antacid tablets have a better acid neutralizing ability than baking soda because
antacids also consist of other chemical ingredients, which may affect the neutralization process. All
antacids will not be equally effective because they generally consist of different chemical ingredients.
The greater proportion of the active ingredient with stronger base in an antacid tablet will have the
greater neutralizing power. Also, the less the number of drops of acid required to neutralize 1 gram of
antacid, the greater is the chance that the antacid is effective to cure upset stomach.
Materials
 Safety goggles
 100 - ml beakers
 Distilled water
 10-ml graduated cylinder
 Hydrochloric acid approximately 2.5% or 1.3 mol/L, pH 1.5
 Sodium bicarbonate (baking soda)
 Electric balance
 5 different antacid tablets
 Red Cabbage Juice
 Mortar and pestle
 Tissue
 Ph sensor and GLX port
 Ph buffer of pH 4 and pH 8 to calibrate
 Flask
Helbig 3

4. [TESTING ANTACIDS] March 11, 2010
*Note: Red Cabbage Juice was used instead of Universal indicator.
PROCEDURES / METHODS
Safety Precautions
• Used eye protection (safety goggles) at all times, until the lab space has been cleared.
• Long hair or loose clothes, were tied back or confined.
• Coats were placed in a locker or were kept away from lab area. Extra books, purses, etc. were kept
away from equipments.
• Glassware were checked for cracks and chips. Cracks could cause the glassware to fail during use
and cause serious injury to lab mates.
• Equipments were not used unless trained and approved as a user by the supervisor.
• Work area was kept clear of all materials except those needed for experiment.
• Labels were read carefully.
• HCl was diluted because it is corrosive and can damage eyes and cause skin irritation.
• All chemical materials were placed away from the table edge.
• Every chemical was treated as if it was hazardous.
• Spills were cleaned immediately (If spill contained very hazardous substance teacher/supervisor
were asked to consider the spill).
• Lab space was kept clean and organized.
• Solvents were not allowed to come in contact with skin.
• Unobstructed access to all exits, fire extinguishers, electrical panels, emergency showers, and eye
washes was maintained.
• Upon completion of the experiment, all chemicals were safely disposed of in the sinks.
• Glassware were washed thoroughly.
• Wastes were disposed correctly.
• The work area should was cleaned up before leaving.
• Hands were washed before leaving the lab and before eating.
Procedure
1. Eye protections (safety goggles) were used at all times, until the lab space has been cleared.
2. Long hair or loose clothes, were tied back or confined.
3. Coats were placed in a locker. Extra books, purses, etc. were kept away from equipments.
4. All the required glassware and other equipments (e.g. 10-ml Graduated cylinder, 100 - ml Beaker,
pipette, flask, Tissue, Mortar and pestle, Electric balance) were gathered.
5. Glassware were checked for cracks and chips because cracks could cause the glassware to fail
during use and cause serious injury to lab mates.
6. The Antacid tablets were acquired and a note was made on the initial observation on the appearance.
7. The total mass of the tablet was weighed using an electric balance and the data was recorded.
8. An antacid tablet was transferred to a clean mortar and crushed to a fine powder using a pestle. A
note was made on the initial observation on the action of crushing the tablets.
9. The crushed tablet was massed out on a tissue paper (teacher instructed how much the mass of each
tablet should be). Then the data (mass) was recorded.
10. The antacid was dissolved in 10ml of distilled water in a 50ml Beaker. Then a note on the initial
observation on the appearance of the solution was mad.
11. To the 50ml beaker of water and antacid a drop of red cabbage juice was added. Then a note on the
initial observation on the appearance of the solution was made.
Helbig 4

5. [TESTING ANTACIDS] March 11, 2010
12. A small beaker of diluted acid (HCl) was acquired. Then two sheet of white paper was placed under
the two beakers.
13. A pipette was used to add acid (HCl), drop by drop to the beaker of antacid and the number of
drops required to get a pH of 2 (until the solution becomes pink) where counted and recorded. The
beaker was swirled until the antacid and acid were mixed thoroughly.
14. Steps 6-13 were applied for all antacid tablets.
15. The work area should be cleaned up before leaving.
16. Hands should be washed before leaving the lab and before eating!
OBSERVATIONS
Table 2. Titration of Antacids without Average = #drops / grams
Antacid Mass of Tablet (g) Drops of Acid Initial pH of Solution Final pH of Solution
Required to see a (without acid) (with acid)
change
Baking Soda 0.5g 200 9 2
Rolaids 1.47g 354 10 2
Eno 1.62g 69 6 2
Gaviscon 0.5g 115 8 2
Tums 1.53g 120 10 2
*Note: The pH number for Initial pH of Solution (without acid) is the highest number of the range. For an
example: if the pH is 7 – 8, the pH must be recorded as 8.
Table 3. The Qualitative Observations – (Short Form)
Antacid Antacid after it Antacid + Antacid + water + Antacid + water +
was crushed water cabbage juice cabbage juice + (HCl)
Baking Soda White, thin Clear liquid Blue, thin liquid Clear solution
powder
Rolaids White, thin Clear liquid Light blue, thin liquid Cloudy solution, bubbles
powder of gas formed
Eno White, thin Clear liquid Light purple, thin liquid Clear solution
powder
Gaviscon White, thin Clear, very thin Very light/purple liquid Cloudy, clumpy (gelatine
powder liquid like)
Tums White, thin Clear liquid Light blue, thin liquid Cloudy solution
powder
*Note: Baking Soda already a came in a powder form.
Table 3. The Qualitative Observations – (Detailed Description)
1 Baking Soda Baking soda is a white powder. When the baking soda and water was mixed, the solution was
clear. When the baking soda was combined with the indicator the solution turned a blue-green
colour.
2 Tums Tums tablet is white in colour. When Tums was added to water, the solution became cloudy
Helbig 5

6. [TESTING ANTACIDS] March 11, 2010
milky white liquid. When the indicator was added, the solution turned blue. When the acid was
added it turned faded pink colour.
3 Rolaids Rolaids is white in color. When added to water, the solution turned cloudy in color. When the
indicator was added, the solution turned a turquoise color and when the acid was added it turned
into faded pink in color.
4 Eno Before Eno was added to water, it was white powder. After adding the powder to water, the
solution remained clear however bubbles began to form. When the indicator was added, the
solution turned blue and when the acid was added it turned pink.
5 Gaviscon Gaviscon was white in colour. When it was mixed with water, the solution turned cloudy. When
the indicator was added, the solution became light blue-green in colour and finally when it was
added to the hydrochloric acid it turned pink.
ANALYSIS
Calculations for Average Drops of Acid Required
Equation used to calculate Average Drops of Acid required for each Antacid:
Antacid Calculation
Baking Soda
Rolaids
Eno
Gaviscon
Tums
Helbig 6

7. [TESTING ANTACIDS] March 11, 2010
Table 4. # of drops / gram (for each Antacid)
Antacid Average = #drops / grams
Baking Soda 400 drops/gram
Rolaids 240.82 drops/gram → 241drops/gram (rounded)
Eno 42.59 drops/ gram → 43 drops/ gram (rounded)
Gaviscon 230 drops/gram
Tums 78.43 drops/ gram → 78 drops/ gram (rounded)
Error Analysis
Errors that might have occurred during the practical lab are:
1. Some ingredients in the antacid may affect the pH value of the mixture and the result.
2. Loss of active ingredient during transferring.
3. The antacid tablet is not crushed properly, so larger particles take longer to dissolve.
4. The other ingredients may affect the solubility of the bases inside the antacid.
5. The reaction may not be complete.
6. The mixture was not stirred properly as the acid was added.
Improvements to the source of errors:
1. Sufficient time should be given for the reaction of acid and base.
2. pH metre should be used to detect the end point of the required pH. (Advantage of pH meter is
that the data will be accurate.)
3. Paying closer attention to the changes of the solution.
Discussion
Stirring is major part of the lab because this activity gives a somewhat accurate data for the
antacids. There would have been a problem, if the mixture was not stirred as the acid (HCl) was added
because the mixture may not get mixed thoroughly and some part of the liquid may still remain acidic.
In other words, only few particles of the acid react with the particles of the base and the rest would be
unable to neutralize the acid, to accurately measure the pH of 2, resulting in an incomplete
neutralization reaction which will display incorrect data. So stirring the mixture as the acid is added, is
vital/ necessary for the somewhat accuracy of the data. Another major part of the lab is the indicator
(used red cabbage juice instead of universal indictor) this is because the lab was supposed to be similar
to the neutralizing acid in a human stomach. Since the stomach has an approximate pH level of 2, all the
antacid tablets are supposed to be measured the pH of 2, using HCl. However, just adding HCl into the
antacid+ water solution does not indicate the pH level, because the solution stays clear or just fizzes. In
order to determine whether the pH is 2, an indicator is required, where color changes occur depending
on the pH level. Therefore, the color of the indicator changed when the acid was added because it
demonstrated that pH of the mixture is not neutral any more (it is either basic or acidic). To make it
easier, scientists tested the pH indicator and verified which color represents what pH level/ number.
There is a variety of antacids available to people and each have different characteristics to satisfy the
customer's preferences. For a scenario, would someone want an antacid to dissolve in the stomach
instantly or over a period of time? The most reasonable answer would be, over a period of time. This
Helbig 7

8. [TESTING ANTACIDS] March 11, 2010
option would be a better choice because the stomach lining is replaced every few days and if the antacid
dissolves instantly it can cause other side effects. This is because the stomach is accustomed to
dissolving substances over a period of time. As stated above, to satisfy the customers' preferences, same
medications are produced in the form of a liquid and in a form of a solid (tablet). However each type
has its own benefit. One possible advantage of liquid medicines over solid medicines is that it takes its
effects really quickly. In other words, it can react faster and can bring results faster, but the solid
medicine will take some time to dissolve. On possible advantage of solid medicine over liquid medicine
is that it does not have unpleasant tastes, like the liquid medicine. When choosing an antacid, there are
things that should be taken in consideration, things such as, ingredients that might trigger allergic
reactions, the pH level of the tablet and the cost. Cost is just a minor thing to consider, but it is
important because someone could purchase an antacid for $50 and it might not even be useful.
Conclusion
The purpose of this investigation was to determine if the different types of commercial antacid
tablets were effective, meaning that they did not neutralize too much or too little of the stomach
solution. As the hypothesis states baking soda (NaHCO3) and Rolaids (CaCO3+ Mg(OH)2) require the
most acid (HCl) to neutralize 1 gram of antacid (see Table 4. for evidence). In addition all antacid are
not equally effective because antacids consist of other chemical ingredients, which may affect the
neutralization and quicken or slow down the process. It is also important to know that if there is a great
proportion of the active ingredient with stronger base in an antacid tablet, the neutralizing power will be
greater. After conducting this investigation the hypothesis was proven to be right. The baking soda
neutralizes more HCl (stomach acid), however it turns out to be that antacid tablets (Eno, Tums,
Gaviscon) were much effective because of the less number of acid require for neutralization. Refer to
Table 4. , baking soda neutralizes a lot of acid and since it is biologically not recommended to
completely neutralize the acid content in the stomach, baking soda is not effective neither beneficial.
For a scenario, if a person would consume too much of baking soda at a daily basis, that individual
could actually be in danger of changing the pH of the stomach and blood. At the same time that
individual can become vulnerable of being a victim of more serious health conditions. This is because
the frequent intake of baking soda irritates the throat and stomach lining. Therefore, antacids are a better
choice for stomach ulcers and heartburn, especially Eno and Tums. These two antacids only require a
small amount of HCl (Eno - 43 drops/ gram & Tums -78 drops/ gram).
Helbig 8