Aleena Parpia
University of Central Florida
October 12th, 2018
Analysis of Neutralizing Ability of Various Antacids
Introduction
The purpose of this lab experiment was to determine the most effective neutralizing stomach antacid by using varying concentrations of HCl and NaOH. The principles of neutralization reactions revolve around combining a strong acid and a strong base to form a product at pH 7. This lab was designed to utilize knowledge of neutralization, and apply it to a lab protoco, to investigate and find the most potent antacid. The neutralizing stomach acids with which each group in the lab experimented on were the following: Gelusil, Alka-Seltzer, Medi-first, and Alcalak.
Antacids are compounds used to alleviate stomach pains, aches, or heartburn. These symptoms can be caused by acid build-up in the stomach. Antacids relieve stomach pain by neutralizing the acid in the stomach, thereby stopping acidic build-up. One of the most common and effective neutralizing stomach acids or antacids is TUMS. The primary ingredient in TUMS is calcium carbonate. Other common antacids are Rolaids, Pepto-Bismol, and Alka-Seltzer. The last antacid, Alka-Seltzer, was used during the experiment. The two most important components of a neutralization reaction are acids and bases. In regard to acids and bases, an acid is a substance that has a pH value of less than seven whereas a base has a pH value greater than seven. Knowing what pH is and knowing where certain substances or enzymes fall on the pH scale is important in regard to our body. Our body is at a pH of 7.4 and if our body shifts below that pH or above that pH, it can affect your overall health. Eating certain food can stray your body out of balance which is why we use certain substances to bring our body back into that state of equilibrium or balance [1]. The lab manual defines each by stating, “an acid is a proton donor and a base is a proton acceptor.” This statement is true when referring to the Brønsted-Lowry definition of what an acid and a base is. However, there is another theory about acids and bases known as the Arrhenius Theory. The Arrhenius theory states that acids dissociate in water to form a hydrogen ion, and bases dissociate in water to form a hydroxide ion. When an Arrhenius acid and an Arrhenius base react together, they form salt and water. This reaction is known as a neutralization reaction. In a neutralization reaction, the acid and the base must be considered “strong” to produce the products of salt and water [2]. The relevance of knowing how to conduct a neutralization reaction is essential for this experiment. The acid-base equation is used to determine how many moles of NaOH will be needed to perform the experiment. Furthermore, it will indicate how many moles of HCl will be neutralized. Hence, knowing the ratio of moles of NaOH used to moles of HCl neutralized will enable the determination of which neutralizing antacid is the best for relieving stomach pains.
The specific aim of the experiment was to design a lab protocol for a titration experiment, in which various concentrations of NaOH and HCl were used. Other constituents that were used were: a specific antacid, Alka-Seltzer and a chemical indicator, phenolphthalein. These substances were used in an experiment to indicate which antacid is the best at neutralizing stomach acid.
Experimental Methods
During this experiment, different types of neutralizing stomach acids were tested to determine which antacid is most successful in neutralizing the build-up of stomach acid. For this particular experiment, Alka-Seltzer was used. First, 125 mL of hydrochloric acid (HCl) was transferred into a beaker using a volumetric pipette. Then one Alka-Seltzer pill was crushed up with a mortar and a pestle and was then mixed into a beaker with the HCl. Next, the solution was separated evenly among five Erlenmeyer flasks, each flask holding 25 mL of solution. For one minute, the Erlenmeyer flasks were heated on a hot plate—at 70 degrees Celsius—in order to evaporate the carbon dioxide. The flasks were then taken off the hot plates and left to cool at room temperature. After the flasks had cooled, three drops of phenylalanine were added to the HCl and antacid solution in the E. flasks. Phenylalanine was the chemical indicator used to titrate the strong acid into a weak conjugate base. The buret was rinsed with deionized water. It was then rinsed with NaOH to balance out the neutralization reaction. Next, the stir bars were placed inside the flasks; the flasks were placed on the hot plate, which was then turned on to 300 kpms. The E. flasks were titrated drop by drop with NaOH until the solutions turned light pink. The results of how many drops of NaOH were used in each titration were recorded in a table. The table also noted the initial volume, final volume, mL used, molarity of the base and the moles of the base used. Once the average of the 5 flasks were calculated, the average number of moles of base (NaOH) were found and recorded. The average number of moles from this experiment, using Alka-Seltzer as the neutralizing acid, was then used as one part of the whole class’s data table. The rest was calculated using other antacids by other groups and all placed in one table.
Results
Table 1: The data below was collected by our individual lab group. These were the titration data and molar calculations for the antacid Alka-Seltzer.
Trail Initial Volume (mL) Final Volume (mL) NaOH Used (mL) Molarity of NaOH (M) Total NaOH (moles)
1 20.0 mL 29.0 mL 9.0 mL 0.25 M 0.00225
2 29.0 mL 38.8 mL 9.8 mL 0.25 M 0.00245
3 38.8 mL 47.9 mL 9.1 mL 0.25 M 0.00227
4 25.0 mL 34.0 mL 9.0 mL 0.25 M 0.00225
5 34.0 mL 43. 9 mL 9.9 mL 0.25 M 0.00247
Table 2: The table below notes the results of the data collected during our experiment. These averages are directly related to all the antacids tested. Each group was in charge of finding these averages through their own individual experiment. This data was then used to compare the antacids and determine which one would be the best neutralizer.
Antacid tested Average moles of NaOH
Gelusil 0.00222
Gelusil 0.00222
Alka-Seltzer 0.00234
Alka-Seltzer 0.00221
Medi-first 0.00227
Medi-first 0.00205
Alcalak 0.00209
Alcalak 0.00219
Discussion
The specific aim of this lab was to determine which antacid had the best acid neutralizing capability. The end point or the equivalence point in a titration experiment is when the moles of titrant are equivalent to the moles of the titrand [3]. Therefore, when the moles of base, NaOH is equivalent to the moles of acid, HCl. This creates a one to one ratio. The equivalence point or end point is used because it determines when and how much of the chemical indicator, in this case phenylalanine, can be used until the solution changes color. It can be concluded from the results—regarding the average number of moles of the base used to neutralize the “stomach-antacid” solution—that the solution containing the antacid, Alcalak, needed the least number of moles of NaOH for completion of titration. It can therefore be discerned that Alcalak neutralized the most moles of stomach acid when compared to other antacids and can therefore be considered, among the given antacids, to be the best antacid for neutralizing overly acidic stomachs. Alcalak’s average number of moles of NaOH was 0.00214 moles. Trailing close behind, Medi-first’s average number of moles of NaOH used was 0.00216 moles. As seen in the results section, Medi-first is the second-best neutralizing agent. These two antacids were very close in neutralization capability, so it can be stated that either one would be an effective neutralizing agent against the stomach’s acidic environment. Errors occurring during this experiment could have also contributed to Alcalak being considered the best neutralizing agent and Medi-First being considered the second best. In another experiment with slightly different results, the conclusions could have been reversed, especially since the data numbers of average moles of NaOH used were so close. Regarding errors and sources of deviations, could have occurred in various aspects of the experiment. One error could have been putting too many drops of NaOH, so the solution turns too pink. There is also no standardization to determine when the solution is the right shade of light pink to stop the titration and conclude that full neutralization had occurred. Also, if the buret had not properly been rinsed first with deionized water, followed by NaOH, the data values could also have been affected.
Conclusion
In conclusion, from our results, Alcalak was the antacid that was best at neutralizing stomach acid. By analyzing the data, it can be suggested that Alcalak uses the least number of moles of NaOH. This also means that the most moles of HCl were neutralized during this specific titration experiment. Overall, the effects of Antacids have proven to positively affect individuals suffering from stomach pains. Using the methodology of this experiment, future experiments can be used to determine the effects that other ingestible drugs can have on the pH of the stomach.
References
[1] “The Importance of PH.” ESKA Water, www.eskawater.com/the-importance-of-ph-2/.
[2] (No Author), Antacid Analysis and the Determination of Percent Acetic Acid in Vinegar: Experiment 15 from General Chemistry Laboratory Manual, 2006 pg. 52-65
[3] Gillespie, Claire. “Definition of Endpoint Titration.” Sciencing, 15 May 2018,
sciencing.com/definition-endpoint-titration-5172167.html.
https://sciencing.com/definition-endpoint-titration-5172167.html