Effectiveness of Antacids
The Purpose
The purpose of this lab was to determine which brand of antacid is more effective at neutralizing hydrochloric acid, the same type of acid that is in the stomach. My partner and I chose to test and compare Tums Extra Strength chewable tablets and Alka-Seltzer Extra Strength Heartburn Relief Chews.
Antacids can neutralize acid chemically with bases such as carbonates and bicarbonates or they can neutralize the acid by absorbing it with ingredients such as magnesium salts. (1) Both antacids that we tested had 750 mg of calcium carbonate as the active ingredient. Calcium carbonate works to chemically neutralize stomach acid to relieve heartburn (2). The neutralization reaction of calcium carbonate and hydrochloric acid is: CaCO3(s) + 2 HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g) (2).
Stomach acid typically has a pH of 1-3 (3), the hydrochloric we used to represent stomach acid had a pH of about 1.41 so it accurately represented the pH of stomach acid. To most accurately represent how antacids behave in the stomach, we also crushed up the Tums and the Alka-Seltzer as if they had been chewed.
The Process
First, we had to measure the pH of the straight hydrochloric acid in order to determine what effect, if any, the antacids had on it. Next, we used the mortar and pestle to crush up 2 Tums tablets and 2 Alka-Seltzer chews, which was the suggested dosage of each antacid. Roughly crushing them was meant to represent as if they had been chewed, as they would if someone was actually taking them. On the first trial, after stirring for 30 seconds, we measured the pH of both the Tums solution and the Alka-Seltzer solution, and although there was significant change in the pH of the Tums solution, there was barely any change in the Alka-Seltzer solution, so we chose to leave each solution overnight after every trial to give each antacid a fair chance.
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Trial 1 Trial 2 Trial 3
Immediate
Immediate
Immediate
5.54
5.43
5.46
Overnight
Overnight
Overnight
6.41
6.41
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Tums Extra Strength
Alka-Seltzer Extra Strength Heartburn Relief Chews
Overnight
Overnight
Overnight
6.22
6.21
6.49
Immediate
Immediate
Immediate
1.64
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Trial 1 Trial 2 Trial 3
The Alka-Seltzer chewables behaved differently than the Tums tablets when we crushed them with the mortar and pestle. The pestle only flattened the chewable tablets into hard, flat disks, which did not dissolve when placed in the hydrochloric acid and stirred. Although the tablets did not dissolve immediately, the hydrochloric acid quickly changed color from clear to the color of the tablet. Because it did not dissolve upon first contact with the acid, it had very little impact on the pH of the acid, which is reflected on the table above. Because of this, we chose to let the tablets dissovle overnight before measuring the pH. The next day when we measured the pH, there had been a greater than before.
Results
The Tums tablets were very easy to crush and crumbled easily under the pressure of the pestle. When mixed with the hydrochloric acid, they caused some slight fizzing and bubbling and immediately changed the color of the acid to the color of the tablet. With stirring, they dissolved very quickly. Immediately, the Tums tablets had a substantial impact on the pH of the hydrochloric acid, jumping just over 4 values, as indicated above, but when we left it overnight, the pH rose more, indicating that the antacid was still working to neautralize the pH.
Product
Materials
Mortar and Pestle (4)
100 mL Beaker (5)
Graduated Cylinder (6)
pH Meter (7)
Hydrochloric Acid (8)
Glass Stirring Rod (9)
Weigh Boats (10)
Alka-Seltzer Extra Strength Heartburn Relief Chews (11)
Tums Extra Strength Tablets (12)
Antacids + Hydrochloric Acid
From our experiments, it can be determined that immediately, the Tums Extra Strength Tablets are more effective at neutralizing stomach acids and providing heartburn relief. This is determined because, after 30 seconds, the Tums raised the pH of the hydrochloric acid from 1.41 to an average of 5.49, whereas, after 30 seconds, the Alka-Seltzer tablets only raised the pH from 1.41 to 1.64, a 0.23 increase compared to the immediate 4.08 increase caused by the Tums.
Although we determined that immediately the Tums Extra Strength Tablets are more effective, over a longer period of time, overnight, the Alka-Seltzer Extra Strength Chews were equally as effective. Based on a percent variate of 4.44% and a range of 0.28, we determined that the range of pHs for the Alka-Seltzer chews was 6.17-6.45, which overlaps with the range for the Tums which was 6.41, determined by a percent variation and range of 0.
Both the Tums and the Alka-Seltzer contained 750 mg of calcium carbonate as the active ingredient, however, because they were in different forms, they worked differently. Alka-Seltzer contained inactive ingredients such as white wax, vegetable oil, and coconut oil, which were most likely in the outer coating of the product. Because the Alka-Seltzer contained these extra ingredients and an outer coating which needed to be dissolved, it worked slowed than the Tums, which immediately dissolved in the hydrochloric acid.
Reflection
A source of error in our experiment is the times that we measured the pH of each trial. The three trials were done over a series of 3 different days and the time between initially mixing in the antacids and measuring the pH was slightly different each day. Because the amount of time slightly varied, the pH measurements were not as accurate as they could have possibly been. In order to solve this problem in a future experiment, we should mix each antacid into the hydrochloric acid at the same time each day and measure the pH also at a set time, or make sure the same amount of time elapses between measurements rather than starting and ending at the exact same time.
In my research, I learned that there are 2 types of antacids, ones that chemically neutralize acids with bases such as carbonates and bicarbonates (1) and ones that absorb acid, such as magnesium salts (1), I think an interesting future experiment would be comparing the effectiveness of antacids that work to neutralize stomach acid chemically and ones that neutralize stomach acid by absorption.
Alka-Seltzer Extra Strength Heartburn Relief Chews (11)
Tums Extra Strength Tablets (12)
