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Analysis of a Stomach Antacid Tablet

Terms in this set (21)

Obtain 100 mL of standard HCl acid solution . Record the molarity of the standard acid. Take a clean buret, rinse it out with a 10 mL portion of your standardized hydrochloric acid, and mount the buret in the clamp on the buret stand. Then fill the buret and bring the level to zero or below by allowing some solution to run out through the top, making certain that no bubbles of air remain in the tip. Wipe the drop of solution off the tip. Place one of the antacid tablets (crush it first with a mortar and pestle) furnished by your instructor in a 250 mL conical flask, add 50 mL of distilled water to get a solution, or slurry. Remember to record the amount and identity of the active ingredient for each tablet found on the label of the antacid container. After all of the material has been crushed and a slurry is obtained, add 5 mL of cabbage extract indicator. Record the reading on your buret and then begin to add acid slowly to the stirred solution. Initially the mixture of water, antacid and indicator will be light green. This will quickly change to purple as acid is added. However, the endpoint is not until a second change of color, from purple to rose/red. Place a sheet of white paper under the flask so you can observe the color changes more easily. The reaction between the acid and these weak bases is slow, so it is important that you add the acid in small fractions, and allow time for the reaction to proceed between each addition of acid. As the titration proceeds, reduce the volume of hydrochloric acid you add each time. As you approach the endpoint, each drop of acid will turn the solution red, which then vanishes as you swirl the solution. A red color which persists for about one minute indicatesthe endpoint. When this has been reached, record the buret reading. The volume of the acid is obtained by difference. 47 Repeat this procedure with a second antacid. Weigh approximately 1.2000 g of baking soda, often used as an antacid. Record the exact amount weighed in the table in mg. Dissolve and titrate this as previously.