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Alka Seltzer Tablets

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Percent by Mass of NaHCO3 in Alka-Seltzer Tablets Introduction Determining the percent by mass of sodium bicarbonate in baking soda is important because it demonstrates the relationship between reactants and products. In this specific experiment, it demonstrates the reaction between a base and an acid. It also reveals the effect that a limiting reactant can have on the product that is produced in a reaction. Alka-Seltzer tablets aim to neutralize stomach acid and thereby reduce stomach pain, as well as other painful symptoms. Alka-Seltzer Original tablets contain three active ingredients: citric acid, aspirin, and sodium bicarbonate. When added to stomach acid, the citric acid and the sodium bicarbonate react to form carbonic acid, water and carbon dioxide in the form of a gas. The gaseous carbon dioxide produces the fizz that is characteristic of Alka-Seltzer.1 However, not all of the sodium bicarbonate reacts with the citric acid, as there is excess NaHCO3. The excess NaHCO3 is what works to neutralize stomach acid. When Alka-Seltzer reacts with acetic acid (vinegar) and water as opposed to stomach acid, carbon dioxide, water, and sodium acetate are produced. The excess NaHCO3 reacts with the acetic acid just as it does with hydrochloric acid. Experimental First, a 100 mL graduated cylinder was obtained and filled with 35 mL of water. A pipet was used to attain a more accurate amount of liquid. The water was then poured into a beaker, which was weighed on an analytical balance. Next, an Alka-Seltzer tablet was obtained and the weight measured using the same balance the weight of the beaker was measured on. When both masses were recorded, the tablet was dropped into the water. The liquid was swirled to allow for the tablet to dissolve completely. After the fizzing had stopped, the beaker was once again weighed and the mass was recorded. Each step was repeated seven more times for a total of eight trials. However, with each trial the liquids added to the beaker changed. In each new trial, an additional 5 mL of vinegar was added and 5 mL of water was taken away. Thus, beaker one had 0 mL of vinegar and 35 mL of water; beaker 2 had 5 mL of vinegar and 30 mL of water; beaker 3 had 10 mL of vinegar and 25 mL

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