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The objective of this experiment was to determine the percentage by mass of calcium carbonate (CaCO3) in toothpaste using the back titration technique. A known weight portion of toothpaste was reacted with a known volume and concentration of standard acid solution. After completing the reaction, the resulting solution containing excess acid was back titrated with a known volume and concentration of standard base solution. This determination of excess acid allowed us to calculate the amount of acid that reacted with CaCO3 in the toothpaste sample.
The result of this experiment showed that 19.6% of calcium carbonate was present in the toothpaste sample. In conclusion, CaCO3 constituted approximately one-fifth of the toothpaste sample, indicating that toothpaste is composed of various components such as fluoride, water, and detergent.
The purpose of this experiment is to demonstrate the practical application of the back titration technique. Back titration is a valuable method when encountering issues with forward titration, such as when the analyte is volatile or insoluble in water, when impurities interfere with forward titration, when the endpoint is difficult to identify, or when the analyte reacts slowly with the titrant.
In this experiment, we analyzed a weighed portion of toothpaste to determine the percentage by mass of CaCO3 present in the sample. The back titration technique was chosen because toothpaste is insoluble in water but soluble in acid.
Titration is a volumetric analysis technique used to determine the concentration of an unknown solution by adding a standard titrant to the analyte until neutralization is reached.
Back titration is a variant of titration where an excess of an intermediate reactant (in this case, hydrochloric acid, HCl) is reacted with the analyte (toothpaste, CaCO3). The reaction goes beyond the equivalence point, with the intermediate reactant in excess. The resulting mixture containing excess intermediate reactant is then titrated back with a known volume and concentration of titrant (sodium hydroxide, NaOH). Knowledge of the stoichiometry of the reaction allows us to determine the concentration of the analyte in the original solution based on the amount of reagent used.
The results of the titration are presented in the table below:
|Trial||Initial Burette Reading (mL)||Final Burette Reading (mL)||Volume of NaOH Used (mL)|
The results obtained from the titration experiments have been analyzed, and the percentage by mass of calcium carbonate in the toothpaste sample has been calculated. The calculations were based on the volume of NaOH used and the stoichiometry of the reaction between HCl and NaOH. Any potential sources of error were also discussed, and recommendations for improving the accuracy of future experiments were provided.
In conclusion, the back titration technique was successfully used to determine the percentage by mass of calcium carbonate in the toothpaste sample. The results indicate that approximately 19.6% of the toothpaste is composed of calcium carbonate. This suggests that toothpaste is a complex mixture of various components, including fluoride, water, and detergent. The experiment was conducted accurately, with no significant errors, and the chemical reaction proceeded rapidly and completely. Therefore, the determination of the concentration of the reactants was precise, making this experiment a success.
Based on the results and the experiment's performance, the following recommendations are made for future experiments:
Overall, this experiment provides valuable insights into the application of back titration in analytical chemistry and the composition of common household products like toothpaste.
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