Evaluation of Antacid Effectiveness in Acid Neutralization

Categories: ChemistryScience


As you may or may not know the stomach, as part of the digestive system, breaks down nutrients or prepares nutrients for further digestion in the small intestine. This is accomplished by hydrochloric acid in gastric juices. The pH of HCL is approximately 2, the optimum pH for metabolic processes which occur in the stomach. The hydrochloric acid breaks down for an example carbohydrates by breaking glycosidic linkages. This means that the glycosidic bonds within polysaccharides are broken causing the polysaccharide to break into monosaccharides such as glucose, lactose or maltose.

When the acid concentration of gastric juices is too high, and hence below the optimal pH for digestion, this acidity can cause an upset stomach, indigestion as well as acid reflux. Acid reflux is when chyme, due to excess acid in gastric juices the stomach travels up the esophageal tract which can cause pain and discomfort.

Acid reflux is treated by a variety of antacids which relieve the symptoms by neutralizing the stomach acid.

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Sodium hydroxide, for example, reacts with hydrochloric acid creating sodium chloride as well as water. Antacids neutralize stomach acids by containing alkaline ions of basic compounds which react with the stomach acid in a neutralization reaction. The objective of this investigation is to test to what extent different antacids neutralize hydrochloric acid as a proxy for gastric juices.

This will be achieved by inducing a neutralization reaction between different antacids and hydrochloric acid, determining the pH with a pH probe before and after the reaction, HCL(aq) +base(s)------>water+ salt.

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This is to deduce experimentally, which antacid works best. This is relevant especially for me as I suffer from frequent episodes of acid reflux. In this investigation, I predict that sodium hydroxide will perform the best. This is because sodium hydroxide is the “pancreatogenic antacid”, meaning that it is the base which is released from the pancreas in order to mediate gastric juice acidity.

Research question: to what extent do different antacids neutralize hydrochloric acid solution, as a proxy for gastric juices, when compared to sodium hydroxide.

Materials and Methods


  • Safety equipment: goggles, nitrile gloves, lab coat
  • Antacid samples: novaculol, sodium hydroxide, omeprazole, pepsid
  • Laboratory tools: balance, mortar and pestle, conical flask, spatula, pH probe with GTX port, pH buffers (pH 4 and 7) for calibration, burette, stove
  • Chemicals: 10 ml of 1.00 M HCl(aq), 6 drops of Phenylalanine, 1 Molar solution of NaOH


Reference trial with NaOH:

  1. Apply safety measures contained in the safety section by putting on safety goggles, lab coat and gloves before conducting the experiment.
  2. Pour 10 ml of 1 M NaOH solution into a beaker.
  3. Pour 10 ml of 1 M HCL into a separate beaker.
  4. Transfer the dilute HCL into the beaker in which the NaOH already is present.
  5. Shake gently in order to assure the solutions mix.
  6. Put the container with the solution on a stove for 5 minutes and take it off before the mixture reaches a boil.
  7. Remove the container, containing the mixture, from the stove and let it sit for about 2 minutes.
  8. Add 6 drops of phenylalanine.
  9. Observe color change in order to get a rough estimate of the solutions pH value.
  10. To be accurate and precise, submerge a pH probe and determine the actual pH value.
  11. Discard chemicals in designated bin.

Trials with antacid samples:

  1. Apply safety measures contained in the safety section by putting on safety goggles, robe,and gloves before conducting the experiment.
  2. Weigh sample of antacid on a balance and determine its mass.
  3. Grab a mortar, and proceed to crush up the sample until it is in the form of fine powder.
  4. Transfer powder from the mortar into a conical flask using a spatula or small spoon.
  5. Do this carefully in order to procure the entire sample into the conical flask.
  6. Using a ph probe, determine the ph of the HCL.
  7. Procure 10 ml of 2.00 molar HCL with a burette by squeezing the rubber balloon until sufficient suction has been reached. Titrate the hydrochloric acid against the antacid. Shake the conical flask well, to homogenize the mixture. Add 6 drops of Phenylalanine, a universal indicator, to the mix. Repeat the titration 2 more times. Now to not just get a rough estimate by the color of the solution, using a ph probe again, submerge the ph probe in the solution and determine the exact final Ph.
  8. Record qualitative and quantitative data and put all cleaned instruments back where they belong. Pour mixture into designated chemical waste flask.

Additional assurance trials

If the neutralization reaction yields the same pH across all trials, then another way to determine the efficacy of the different antacids is to determine how many ml of HCL is required to bring the pH of the dissolved antacid back down to 2.

  1. Apply all safety measures outlined in the safety section.
  2. Gather equipments(1 M HCL, antacid samples, GTX pH probe, measuring cylinder, mortar, pestle, balance etc.)
  3. Dissolve a one gram sample of antacid in 50 ml of water.
  4. Calibrate the GTX pH probe.
  5. Submerge the GTX pH probe in the solution.
  6. Now add 1 ml of 1 M HCL every 10 seconds or so, until the pH probe reads that the pH is back down to 2.
  7. Clean all equipments and discard chemicals in designated waste bin.
  8. Collect the data on a sheet of paper.


The experiment produced both qualitative and quantitative data regarding the antacids' effectiveness. Observational data highlighted characteristics such as antacid state, color, and reactions during neutralization, including bubbling and odor emission. Quantitative data focused on the mass of antacid used, concentration of hydrochloric acid neutralized, and pH levels before and after neutralization. The tables below summarize these findings.

Table 1: Raw Quantitative Data

Antacid Trial Mass (g) Concentration of HCl (M) Grams HCl Neutralized Mol HCl Neutralized Grams Neutralized/Grams of Tablet
Novaculol 1-5 1.00 1 M 0.449-0.623 0.0097-0.017 0.449-0.623/1g
Omeprazole 1-5 1.00 1 M 0.435-0.574 0.0113-0.0157 0.435-0.574/1g
Pepsid 1-5 1.00 1 M 0.141-0.376 0.00387-0.01035 0.141-0.376/1g

Table 2: Processed Quantitative Data

Measurement Novaculol Omeprazole Pepsid
Mass (g) 1.00 1.00 1.00
Concentration of HCl 1 M 1 M 1 M
Volume of HCl (ml) 10 10 10
Grams HCl Neutralized (averages) 0.4992 0.5086 0.2846
Mol HCl Neutralized (averages) 0.01354 0.01418 0.00597
Grams Neutralized/Grams of Tablet (averages) 0.4992/1g 0.5086/1g 0.2846/1g


The investigation revealed variations in the neutralization efficacy of different antacids against hydrochloric acid. Sodium hydroxide, as hypothesized, demonstrated significant neutralizing capacity, aligning with its role as a pancreatogenic antacid. The findings underscore the importance of understanding antacid compositions and their reactions with stomach acid, providing valuable insights for individuals experiencing acid reflux and related conditions.

Safety Considerations

The experiment adhered to strict safety protocols, including the use of protective gear and proper disposal of chemicals. Observational data underscored the need for caution due to potential bubbling and odors during the neutralization process.

This comprehensive analysis, incorporating both qualitative observations and quantitative measurements, offers a nuanced understanding of antacid performance, guiding effective treatment choices for acid reflux.



Updated: Feb 16, 2024
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Evaluation of Antacid Effectiveness in Acid Neutralization. (2024, Feb 16). Retrieved from https://studymoose.com/document/evaluation-of-antacid-effectiveness-in-acid-neutralization

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