Research Question: How to compare two types of Antacids, Eno powder and Tumms, to determine which neutralizes the maximum moles of Hydrochloric acid in the stomach using back-titration of 0.5M of HCl and 0.5 M of NaOH?

General background: Indigestion, also known as dyspepsia, is a term used to describe one or more symptoms including a feeling of fullness during a meal, uncomfortable fullness after a meal, and burning or pain in the upper abdomen. Antacids are usually the first drugs recommended to relieve symptoms of indigestion.(


Here, A fixed volume, 25 cm3of 0.5M of standardized hydrochloric acid is placed in a conical flask. Then, a maximum daily dosage of Eno or Tums is added to the hydrochloric acid in the flask. The antacid that is supposed to neutralize some of the excess hydrochloric acid of the stomach will neutralize some of the excess hydrochloric acid in theconical flask. Theunreactedhydrochloric acid, if any, will be neutralized using 0.5 M standardized aqueous sodium hydroxide from a 50 cm3burette. Using the volume of base needed to neutralize the excess acid, we will be able to calculate the amount of acid neutralized by the individual antacids, hence enabling us to compare their relative effectiveness. One Sachet of Eno contains Sodium Bicarbonate and Citric acid while one tablet of Tums contains Calcium Carbonate.The Tums I predict will neutralize more HCl acid than Eno as even though both Sodium Bicarbonate and Calcium Carbonate neutralize 2 moles of HCl because Eno also contains Citric Acid, which will counteract its neutralizing effect. Therefore the sodium hydroxide will have to neutralize less excess acid to reach the equivalence point when using Actal Tums, as compared to the maximum dosage of Eno.



q Source of Antacid (Eno or Tumms)


q The moles of HCl neutralized by each antacid


q Concentration and Volume of HCl used

q Amount of each Antacid per trial: 2 Tablets of Tumms and 1 Sachet of Eno

q Concentration of NaOH used


q Two 250 cm3conical flask

q 50±0.05cm3burette

q Filter funnel

q 25±0.06cm3pipette

q Metal clamp stand

q Two 250 cm3 glass beakers

q A glass rod


q 3 Eno sachets (4.5 grams each)

q 6 Tums Tablets (500mg each)

q Distilled water

q Few drops of Phenolphthalein indicator

q 250 cm3 of Aqueous standardized 0.5M Hydrochloric acid

q 150 cm3 Aqueous standardized 0.5M Sodium hydroxide base


1. Fill the 50cm3burette with aqueous sodium hydroxide (0.5M) till the 0 cm3mark is reached using the filter funnel.

2. Take 25cm3 of the prepared 0.5M solution of HCl with the help of a pipette in the 250cm3conical flask.

3. Dissolve two Tumms tablets in the HCl solution in the flask

4. Stir using a glass rod until the tablet has dissolved completely.

5. Using the funnel add 3-4 drops of Phenolphthalein indicator to the conical flask.

6. Start adding the NaOH solution 1 cm3 at a time to the flask from the burette.

7. Stop as soon as the mixture in the flask changes color from colorless to pink.

8. Record the final volume reading of NaOH in the burette.

9. Repeat the same experiment twice and take an average.

10. Repeat the procedure from 1-9 for Eno powder using one sachet for every trial.

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