Acid Was Considered To Neutralize Two Tablets Of TUMS T

In this experiment, we took two TUMS tabs and through a back titration, we were able to find out how much acid was needed to neutralize two tablets of TUMS. In the first process of the titration, we added excess HCl and then we had to back titrate it by adding NaOH. We had to do a standardization test because the NaOH has a high reactivity and that could cause a small change. The NaOH solution was supposed to have a molar concentration of .5 however when we standardized the solution we found the actual molarity of the solution to be .4761. This may be due to the fact that NaOH is almost impossible to have pure because it reacts with CO2 in the air. Strong bases are generally very reactive and it makes it hard to have a pure solution of NaOH
which would correspond to why we had a lower molarity calculated from the actual molarity. Sodium hydroxide is deliquescent and it absorbs water from its surroundings.
As the NaOH reacts with water from its surroundings, the moles of NaOH would decrease and that would also bring the molarity down. For our standard acid test we used KHP which also helped to eliminate errors. KHP is a weak acid and therefore it has less reactivity. Our KHP was in a solid and dry powder form which allowed us to mass it out using the scale. Because it was a solid, this got rid of the error of evaporation to occur and led us to be more accurate with out results. We also used a compound with a high molecular mass. The KHP had a molecular mass of 204.23 g/mol. If the compound had a low molecular mass, there would be a significant change if we were off one or two grams which would be a big error. The phenolphthalein that we added helped us decide when we added enough base to neutralize the excess H+’s in the HCl solution. We saw the color change occur when 22.9 ml were added to the solution. If we had added any more of the NaOH we would have went greatly past the endpoint which would be an unsuccessful titration and the hue would become a very dark pink. Even though the phenolphthalein is a useful color indicator, if we added too little of it we might have not been able to tell at the exact moment when the color change took
place. Our calculations suggest that there was 727.5 mg CaCO3 in one TUMS tablet. The label said that there would be 750 mg of calcium carbonate but our experiment led us to believe that there is actually a lower amount of calcium carbonate present in each tablet. We could have a lower value because it is just the batch that we had and the TUMS company did not add a lot of calcium carbonate to its sample. The company could possibly say that there is 750 mg of calcium carbonate added, but in order to increase consumers, they may have added other substances to the calcium carbonate in order to have a better flavor.