UCSB CHEM 1AL - Experiment 8: Antacid Analysis Discussion

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Chem 1BL F 1 00 4 50 Dee Saenz 02 05 2024 Experiment 8 Antacid Analysis Discussion The overall purpose of the lab is to assess an antacid tablet s effectiveness with acid base titration The objective of this experiment was accomplished by using titration with an antacid which was a tums tablet neutralized by a strong acid HCl Lastly we titrated the solution with a PH indicator 0 1 phenolphthalein and a strong base NaOH to help shift to equilibrium in which then we were able to calculate the mass of CaCO3 in the antacid tablet Lastly a general method to use was to make sure to use a stopper with NaOH to not allow CO2 to alter the results We determined the mass of calcium carbonate s by mixing an antacid tums tablet with 0 3 M hydrochloric acid and allowing it to dissolve in the solution This allowed calcium carbonate which is the base in the antacid to dissolve since it is insoluble in water meaning it will stay a solid CaCO3 s Ca 2 aq CO3 2 aq The value of Ksp is Ksp Ca 2 CO3 2 8 7 x 10 9 We are not able to dissolve calcium carbonate s in water because it is relatively insoluble and it would need to dissolve to raise pH by reacting with We also can not do a direct titration with hydrochloric acid because in a neutral solution calcium carbonate remains very insoluble thus the carbonate anion does not dissociate and therefore does not react with in the solution Therefore dissolving the antacid in hydrochloric acid helps the solution to react completely This helps us accurately figure out how effective the antacid is The back titration with sodium hydroxide helped us figure out how much acid is still left after the antacid has done its job This way we can calculate how well the antacid works We detected the end point in titration by using a 0 1 phenolphthalein indicator which turns the solution pink CaCO3 s 2HCl H2C03 aq CaCl2 aq The net ionic equation is CO3 2 aq 2H aq H2CO3 aq when we have reached a basic pH HCl aq NaOH aq H2O l NaCl aq Net ionic equation H aq OH H2O l The purpose of doing the titration is to help us find out how much of something is in a solution At the end of titration we figure out exactly how much of the solution we need fully react with the substance we re testing This helps us calculate how much of the substance is in the solution At the end NaOH reacts with any HCl remaining in the solution after the antacid has done its job By measuring how much NaOH is used up we can then figure out how much hydrochloric acid reacted with the antacid tablet To find the mass of calcium carbonate we first had to determine the volume of sodium hydroxide that we needed to reach the equivalence point from titration So the first antacid was determined to be 453 5 mg The second antacid was determined to be 327 7 mg The average mass of calcium carbonate is determined to be 390 6 mg with the deviation being 0 219 mg For the first antacid my results are pretty close to the 0 500 mg of calcium carbonate that is supposed to be in each tablet For the second antacid my results are pretty off being in the low 300s mg which could indicate an error in the tablet not dissolving completely in hydrochloric acid For the first antacid the percentage of calcium carbonate in the antacid tablet is 34 39 and the percentage of deviation in mass is 9 30 For the second antacid the percentage of calcium carbonate in the antacid tablet is 24 77 and the percentage of deviation in mass is 34 46 The percentages of calcium carbonate in each of the antacid tablets is less than one hundred percent because there are fillers sugars and other ingredients in the antacid other than just calcium carbonate alone hence why there are 0 500 mg of calcium carbonate For the first antacid the measured amount of calcium carbonate was quite close to the expected 500 mg coming in at 453 5 mg There could be several reasons for any discrepancies Firstly we might not have allowed the antacid enough time to fully dissolve especially considering it contained a lot of starch initially Additionally since it was a Tums tablet it likely contained various additives like sugar and fillers to improve taste which could affect the results In contrast the second antacid yielded only 390 6 mg indicating a clear error on my part We didn t let it heat up sufficiently to dissolve properly although even at higher temperatures it failed to dissolve completely We assumed it had started dissolving but it seems there were issues with the antacid itself potentially due to starch content or additional supplements like sugar fibers etc During the titration process precision is crucial It took a considerable amount of time for the solution to change color and when we were close to the desired light pink shade we added a bit too much titrant illustrating the importance of proceeding slowly and steadily If too much titrant is added during titration the experimental mass of CaCO3 in the antacid tablet can exceed the actual 500 mg due to continued reaction beyond the endpoint Conversely stopping the titration prematurely leads to an underestimation of CaCO3 mass The observed differences in the antacid results particularly the variation between mid 400s and low 300s in milligrams of calcium carbonate underscore the necessity of conducting multiple trials to mitigate the impact of potential errors For instance stopping the titration before reaching the endpoint may have influenced the results for the second antacid Absorption of CO2 gas by the NaOH solution can reduce the available NaOH for neutralizing acid potentially resulting in underestimated measurements This could also explain the lower value obtained for the second antacid Ultimately these discrepancies emphasize the importance of meticulous experimentation especially in titration to ensure accurate results


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UCSB CHEM 1AL - Experiment 8: Antacid Analysis Discussion

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