Hill Antacid Effectiveness Lab
CHEM 002: G1 performed 10/26/06
Logan Hill
Lab Partner: Jason Henderson TA: Ayse Beyaz submitted 10/17/06
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Introduction
This purpose of this lab is to test and compare the ability of a few common commercial antacids to neutralize hydrochloric acid acid (stomach acid). The benefits of knowing this information are multifold. multifold. Manufacturers interests are obvious: to sell a product, one must always work to increase increase its effectiveness to the consumer. Regulating agencies like the FDA look into the legitimacy and safety of commercially sold products like a ntacids. Finally, any good consumer would like to be informed of the “bang for the buck” of the product they are purchasing. Using basic knowledge of chemical equations and stoichiometry, one can determine the strength of a strong base (in this case, one of the antacids) by calculating the amount of strong acid that the base neutralizes. In this lab, both forward (direct) and back (indirect) titration methods are used to ascertain the strength of the antacid. Forward titration titrates the acid directly into an aqueous solution of the antacid, an tacid, using an indicator to signify the end point. Back titration adds the antacid to an excess of acid then titrates a strong base into the acidic solution until it is neutralized. The amount of acid neutralized by the antacid can then be determined by subtracting the amount neutralized by the titrated base from the total amount of acid neutralized. Safety is a substantial substantial issue in this lab. Strong acids (hydrochloric acid) and bases (sodium hydroxide) are very toxic if ingested and can cause severe burns upon contact with skin. Proper attire (approved lab goggles, appropriate clothing, closed-toed shoes) should be worn at all times. Products of the experimental reactions reactions could be harmful to the environment, environment, and thus should be disposed of accordingly. In addition to the dose effectiveness of o f each antacid in the study, the cost effectiveness was also determined. This data is very important to the consumer sector. sector. If an equivalent result
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can be safely achieved between a higher dosage of one antacid at an overall lower price than another more powerful and expensive antacid, it is obviously more advantageous to the consumer to purchase the cheaper product. Considering this, the cost effectiveness of the antacid is more important than the per dose effectiveness, at least as far as the consumer is con cerned.
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Experimental Methods
Three different antacids were chosen for this experiment: Maalox, Rolaids, and Tums. The neutralization capabilities of all three were evaluated using back titration. The Tums was then analyzed again, this time time using forward titration. titration. The recommended dosage (1 tablet) for each antacid was obtained and added to approximately 25 ml of hydrochloric acid in separate Erlenmeyer flasks (the acid was added prior using a buret and the exact amount in each flask was measured to .01 ml). The antacids were then dissolved dissolved in the acid with a combination combination of stirring and heating. Upon complete reaction of the antacids, antacids, three drops of phenolphthalein were then added to each flask. Each solution was individually titrated with sodium hydroxide hydroxide until the first sign of a slightly slightly pink color change. The volume of sodium hydroxide added was recorded as the end point of titration. For the forward titration of the Tums, a Tums tablet was first added to approximately 50 ml of water in an Erlenmeyer flask, then dissolved with the help of heat and stirring. stirring. Fifteen to twenty drops of bromcresol green indicator were added to the solution. The solution was then titrated with hydrochloric acid until the indicator produced a distinctive green color. Upon reaching the end point, the volume of hydrochloric acid titrated was recorded.
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Results and Discussion
Chemical Equations: HCl (l) + NaOH (l) 2HCl (l) + CaCO3 (s)
→
→
NaCl (aq) + H2O (l)
CaCl2 (aq) + H2O (l) + CO2 (g)
2HCl (l) + Mg(OH)2 (s)
→
MgCl2 (aq) H2O (l)
(1) (2) (3)
N acid added = V acid added x M acid
(4)
N base added = V base added x M base
(5)
N acid used = n acid added – n acid leftover
(6)
mg of acid used = mg of HCl neutralized = MW HCl x n acid used
(7)
Antaci Antacid d Effect Effective ivenes nesss = mg of HCl neutral neutralize ized d / recomm recommende ended d dose dose of antaci antacid d Cost Cost Effe Effect ctiv iven enes esss = anta antaci cid d eff effec ecti tive vene ness ss / (co (cost st in doll dollar arss / reco recomm mmen ende ded d dos dose) e)
(8) (9) (9)
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Figure 1. Actual vs. Theoretical Weight of HCl Neutralized 546.8 566.8
600 ) g 500 437.4 393.3 m ( 400 t h g 300 i e W l 200 C100 H
0
x l o a M a
364.5
364.5
415.5
276.7
s k ) d ) d r c i l a b a w a ( o r s R f o ( m s T u m T u Antacid
Theoretica Theoreticall
Actua ctuall
Figure 2. Percent Yield
120% d 100% l e i Y 80% e g a 60% t n e 40% c r e P 20%
114%
104% 90% 76%
0% Maalox
Rolaids Antacid
Tums (back)
Tums (forward)
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Figure 3. Actual Cost Effectiveness per Dollar r 40 e p 35 g m ( 30 s s ) r 25 e a n l 20 e l o v i t d 15 c e 10 f f E 5 t s o 0 C
37.5
34.3 22.9
11.7
Maalox
R olaids
Tums (back)
Tums (forward)
Antacid
Figure 4. Actual Neutralization of HCl (Forward vs. Back Titration) 500
) g m ( 400 d e z i l a r 300 t u e N 200 l C H t h 100 g i e W 0
415.5 276.7
Forward Titration Method
Back
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Data Tables: Table 1. Back Titration Data
Maalox
Initial Volume HCl (ml) 5.92
Final Volume HCl (ml) 30.50
Total Volume HCl (ml) 24.58
Moles HCl (mmol) 30.90
Rolaids
9.42
34.92
25.50
32.05
Tums
6.59
31.54
24.95
31.36
Maalox Rolaids Tums
Initial Volume NaOH (ml) 4.66 15.69 24.51
Final Volume NaOH (ml) 15.31 24.43 37.10
Total Volume NaOH (ml) 10.65 8.74 12.59
Moles NaOH (mmol) 20.11 16.50 23.77
HCl Used (mmol) 10.79 15.55 7.59
Table 2. Forward Titration Data
Tums
Initial Volume HCl (ml) 13.25
Final Volume HCl (ml) 22.13
Total Volume HCl (ml) 9.05
Moles HCl (mmol) 11.4
Table 3. Antacid Active Ingredients
Maalox Rolaids Tums
Active Ingredient
Mass of Antacid (mg)
Calcium Carbonate Calcium Carbonate Magnesium Hydroxide Calcium Carbonate
600 550 11 0 500
Amount of Antacid (mmol) 6 5.5 1.9 5
Table 4. Results Theoretical Actual HCl (mg) HCl (mg) Maalox 437.4 393.3 Rolaids 546.8 566.8 Tums* 364.5 276.7 Tums** 364.5 415.5 *Back Titration **Forward Titration
Theoretical HCl(mmol) 12 15 10 10
Actual HCl (mmol) 10.79 15.55 7.59 11.4
Percent Yield (%) 90% 104% 76% 114 %
Antacid Effectiveness .656 mg/dose .859 mg/dose .553 mg/dose .831 mg/dose
Cost Effectiveness 11.7 mg/$ 37.5 mg/$ 22.9 mg/$ 34.3 mg/$
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Conclusion
It can be seen from Figure 1 above that there were some discrepancies between the calculated theoretical weight and the actual experimental weight of acid neutralized. The error exhibited is not overly large, and is not n ot consistent over the entire experiment. These signs p oint to random error on the part of the experimenters. Random error could consist of continuing past the end point of titration, misreading the buret, or error in calculation. The percent yield obviously exhibits these same symptoms, as seen in Figure 2. Because the error seems to be more random than systematic, a comparison between the effectiveness of the antacids may be inaccurate as based on this experiment. ex periment. In addition to these, a large difference can be seen between b etween the yields from the forward and back titrations. This is shown in Figure 4. It is interesting to point out that the larger error seems to be exhibited in the back titration, though the forward titration is often more difficult to perform accurately. Overall, the experiment went well in terms of procedure. The students were prepared and knowledgeable as to what was required and how they were to go about the lab. Although some error was exhibited, in only one case ca se was it substantially large. This leads the students to believe their results to be acceptable, with most of the theoretical yields within of 15% of the actual yield.
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“Antacid Analysis.” Analysis.” Chem 2. Laboratory Packet. Rolla, MO: UMR Chemistry Chemistry Department, 2006. 6.1-6.6. Chem II Lab Manual University University of Missouri-Rolla. Missouri-Rolla. Brooks/Cole, 2006. Bone, Terry. T-Bone’s Homepage. University of Missouri-Rolla. 12 October 2006
