By: Steve Bintz
Steve Bintz
The Effectiveness of Antacids on HCl
March 13, 2006
Group 4
Proposal (20 points)
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Notebook (15 points)
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Peer/Faculty Evaluation (10 points)
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Report (55 points)
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Project Grade (100 points)
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Abstract (Experimental Summary)
The purpose of this experiment was to determine which of two antacids would be the
most effective in neutralizing hydrochloric acid. This was done by titrating a
standardized solution of acid mixed with an antacid tablet with a standardized base,
sodium hydroxide. When the procedure was finished, the number of unreacted moles of
acid left was used to determine which tablet neutralized the most and was therefore the
most effective. The effectiveness was measured by calculating the amount of acid
neutralized by one gram of the antacid. It was determined that Rolaids was the more
effective antacid because it neutralized .2312g more of the acid. There are several areas
in which errors could be made, however it is believed that these values are accurate due
to multiple trials and the use of averages.
By: Steve Bintz
Introduction of Methods and Terms
One very important technique is necessary to make this experiment possible.
Titration is performed by using one solution to analyze another. 1 In other words, for this
experiment, an acid is titrated with a base in order to find out how much is the most
effective. Titrations involve the use of an indicator to determine when an endpoint has
been reached. An important term throughout this experiment is neutralization.
Neutralization simply means that the pH is being brought closer to 7. It is essentially and
acid-base reaction which produces a salt. A demonstration of this is found during
titration. When an endpoint is reached, it means that all acid or base has been neutralized
and the titrant is becoming an excess in the solution. The use of antacids is to make the
environment less acidic by neutralizing whatever acid is present.
Results and Discussion
A display of the results can be found in the tables below. Sample calculations are found
at the conclusion of the lab report.
Table 1-Standardization of NaOH – from April
Titration
H2C2O4Burette 2nd Reading
H2C2O4 Burette 1st Reading
Volume H2C2O4 Used
NaOH Burette 2nd Reading
NaOH Burette 1st Reading
Volume NaOH Used
Molarity of NaOH
#1
44.00 mL
18.00 mL
26.00 mL
19.50 mL
5.49 mL
14.01 mL
1.118 M
#2
23.00 mL
1.49 mL
21.51 mL
31.20 mL
19.56 mL
11.64 mL
1.113 M
#3
47.00 mL
22.90 mL
24.10 mL
44.20 mL
31.25 mL
12.95 mL
1.121 M
Table 2-Standardization of HCl – from Allison
Titration
NaOH Burette 2nd Reading
NaOH Burette 1st Reading
Volume of NaOH Used
HCl Burette 2nd Reading
HCl Burette 1st Reading
Volume HCl Used
Molarity of HCl
#1
19.19 mL
.08 mL
18.11 mL
41.98 mL
21.35 mL
20.63 mL
.9806 M
#2
37.69 mL
19.19 mL
18.50 mL
20.35 mL
.19 mL
20.16 mL
1.025 M
#3
18.92 mL
.15 mL
18.77 mL
40.89 mL
20.70 mL
20.19 mL
1.038 M
A primary and secondary standard are necessary to have accurate measurements.
A primary standard has the characteristics of being very pure, stable and has a known,
exact molarity. 2 It is necessary to obtain accurate measurements throughout the
experiment, as well as prepare a secondary standard. A secondary standard is a solution
which has been prepared using stoichiometry and the molarity is subsequently
determined using the primary standard. It is necessary to determine the molarity using
the primary standard because often the components are not available in the necessary
By: Steve Bintz
precision. Table 1 and Table 2 show the molarities of sodium hydroxide, the primary
standard, and hydrochloric acid, the secondary standard.
Table 3-Results of Tums Titration
Tablet Titration
Weight of Tablet
HCl Burette 2nd Reading
HCl Burette 1st Reading
Volume of HCl Used
Initial Moles of HCl
NaOH Burette 2nd Reading
NaOH Burette 1st Reading
Volume of NaOH Used
Moles of NaOH Used
Unreacted moles of HCl
#1
1.293 g
22.70 mL
.38 mL
22.32 mL
.02265 moles
13.32 mL
1.88 mL
11.44 mL
.01278 moles
.00987 moles
#2
1.291 g
21.40 mL
.41 mL
20.99 mL
.02130 moles
23.30 mL
13.22 mL
10.08 mL
.01126 moles
.01004 moles
#3
1.303 g
37.00 mL
16.18 mL
20.82 mL
.02113 moles
29.65 mL
19.80 mL
9.85 mL
.01100 moles
.01013 moles
The Tums tablet would be expected to react with acid as shown in Reaction 1:
CaCO3 + 2HCl  CaCl2 + CO2 + H2O
(1)
Table 4-Results of Rolaids Titration – from Kelly
Tablet Titration
Weight of Half Tablet
HCl Burette 2nd Reading
HCl Burette 1st Reading
Volume of HCl Used
Initial Moles of HCl
NaOH Burette 2nd Reading
NaOH Burette 1st Reading
Volume of NaOH Used
Moles of NaOH Used
Unreacted moles of HCl
#1
.826 g
22.63 mL
2.40 mL
20.23 mL
.02053 moles
12.35 mL
1.31 mL
11.04 mL
.01233 moles
.0082 moles
#2
.701 g
21.16 mL
1.04 mL
20.12 mL
.02042 moles
12.18 mL
.30 mL
11.89 mL
.01328 moles
.00714 moles
#3
.778 g
20.35 mL
.20 mL
20.15 mL
.02045 moles
13.08 mL
1.97 mL
11.11 mL
.01241 moles
.00804 moles
One would expect the Rolaids tablet to react with hydrochloric acid as shown in
Reaction 2:
Mg(OH)2 + 2HCl  MgCl2 + 2H20
(2)
The results shown in Table 3 and Table 4 suggest the Tums antacid to be the most
effective. This can be concluded because it neutralized more moles of acid than did
Rolaids. However, there are two areas which must be considered before making a
determination. First, the Rolaids titration, as detailed in Table 4, was done with
approximately one half of a tablet due to an insufficient supply. Here, it is impossible to
obtain exactly one half a tablet and human error becomes a great factor, as shown in the
varying tablet weights. Secondly, there must be a standardized measure to show how
many grams of the acid have been neutralized without having to consider varying
weights. In other words, the weights of the Rolaids and Tums tablets will never be
By: Steve Bintz
exactly equal, so a quantitative measure must be calculated to compare the effectiveness.
These issues are resolved by the calculations summarized in Table 5:
Table 5-Summary of the number of grams of HCl neutralized by 1g antacid tablet
Tums
Rolaids
Trial 1
.3631g
.5443g
Trial 2
.3180g
.6908g
Trial 3
.3079g
.4475g
Average
.3297g
.5609g
Table 5 represents the only way to determine which antacid is more effective.
Here, each tablet is shown in terms of the amount of acid it would neutralize if only using
one gram. This clearly shows Rolaids neutralizes the most acid and is therefore more
effective than Tums.
Experimental error is very prevalent in this experiment. The main place where
error occurs is in the reading of the burettes and the determination of when an endpoint
has been reached, but not overshot. These two mistakes alone can cause a large variance
in measurements as well as make averages falsely represent the data. A loss of tablet
mass was very unlikely due to the care taken and very few other areas for error were
possible, except for simple calculation errors.
This experiment concluded, through acid-base neutralization reactions, that
Rolaids is a more effective antacid than Tums. Titration was the key procedure used
throughout these tests by making standard solutions and determining the number of acid
moles neutralized. Therefore, when looking for the most effective relief of heartburn, our
group suggests taking Rolaids.
References
1) Zumdahl, Steven S., Zumdahl, Susan A. Chemistry: Sixth Edition. Houghton Mifflin
Company: Boston. 2003.
2) Chemistry Department. “Standards” Standard Reference Materials. New Mexico
State University. 6 March 2006
<http://www.chemistry.nmsu.edu/Instrumentation/Standards.html>
Sample Calculations
Oxalic Acid Molarity:
9.488g
| .07530 mol = .3012 M
126.01g/mol | .2500 L
NaOH Molarity:
.3012 mol | .02600 L = .0078312 moles acid | 2 moles NaOH = .0156 mol = 1.118 M
L |
| 1 mole acid
.01401 L
NaOH
HCL Molarity:
1.117 mol | .01850 L = .0206645 mol NaOH=.0205545 mol HCl = 1.025 M HCl
L
|
L
By: Steve Bintz
Initial Moles HCl:
1.015 mol | .02023 L HCl used = .02053 moles HCl
L
|
Moles NaOH Used:
1.117 mol | .01104 L = .01233 moles NaOH
L
|
Unreacted Moles HCl:
Initial Moles HCl – Moles NaOH Used
.02053-.01233 = .0082 moles unreacted of HCl
Comparison for 1g of tablet
.01144 mL NaOH | 1.117 mol | mole HCl | 36.46 g HCl = .4659g HCl neutralized
|
L
| mole NaOH|
mole
.4659g = HCl neutralized = .3631g HCl neutralized
1.29g
1g