What Causes the Fizz When an Antacid Is Added to Water

1 ] What Causes the Fizz When an Antacid Is Added to Water  

The familiar fizzing action that occurs as an antacid tablet dissolves in water is the result of a chemical reaction involving the ingredients in the tablet. 

Each Alka-Seltzer tablet contains 1916 mg of sodium bicarbonate, 1000 mg of citric acid (Fig. 9.1.2), and 325 mg of aspirin or acetylsalicylic acid (Fig. 9.1.3)J Bromo Seltzer also contains sodium bicarbonate and citric acid as well as acetaminophen (Fig. 9.1.4). Several equilibria describe the action of bicarbonate-based antacid tablets. First of all, sodium bicarbonate dissolves completely in aqueous solution to generate sodium ions and bicarbonate ions  

In water the bicarbonate ion is in equilibrium with carbonic acid  

The small value of the equilibrium constant indicates that the formation of carbonic acid is not very extensive in neutral water. However, the formation of carbonic acid is quite favored in acidic solution (arising from the citric acid also contained in the product)  

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What causes the fizz when an antacid is added to water See p. 116. 

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