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The main objective of this experiment was to determine the percentage of calcium carbonate in toothpaste using a back titration approach. Calcium carbonate, an insoluble salt, was reacted with excess hydrochloric acid, followed by back titration with sodium hydroxide. The average percentage of calcium carbonate in toothpaste was found to be 19.2%, which is close to the expected value of 20%. The experiment was performed twice to improve accuracy, revealing that smaller amounts of toothpaste required more sodium hydroxide to neutralize excess hydrochloric acid.
Titration is a common analytical technique used to determine the concentration of a substance in a solution by reacting it with a solution of known concentration.
In cases where the substance is volatile or insoluble, such as calcium carbonate, a back titration method is employed. Back titration involves reacting the unknown substance with an excess of a known reagent and then titrating the unreacted reagent with another reagent.
Toothpaste typically contains approximately 20% calcium carbonate, which acts as an abrasive to remove dental plaque and food particles.
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Maintaining the correct percentage of calcium carbonate is crucial to prevent enamel thinning, tooth discoloration, and tooth sensitivity. This experiment aims to determine the actual percentage of calcium carbonate in toothpaste to ensure it aligns with the expected 20%.
The experiment utilizes back titration due to the insolubility of calcium carbonate in water. The reaction involved is as follows:
CaCO3 + 2HCl → CaCl2 + H2O + CO2
Since hydrochloric acid is in excess, only a portion of it reacts with calcium carbonate. To determine the excess hydrochloric acid, it is back titrated with sodium hydroxide (NaOH).
The number of moles of reacted hydrochloric acid can be calculated using the original 10 mL of 0.16M hydrochloric acid minus the excess amount.
Using the stoichiometric equation, the mole ratio between CaCO3 and HCl is 2:1. Therefore, the number of moles of CaCO3 can be determined by dividing the moles of HCl by 2. The mass of CaCO3 is found by multiplying the moles by the molar mass (100 g/mol).
The percentage of CaCO3 in toothpaste is then calculated as the mass of CaCO3 divided by the mass of toothpaste used, multiplied by 100. This value is expected to be close to the literature value of 20%.
Materials:
Procedure:
Based on the experimental data, it was observed that the less toothpaste used, the greater the volume of sodium hydroxide required to neutralize the excess hydrochloric acid. This is because a smaller amount of toothpaste contains less calcium carbonate (CaCO3), leading to less hydrochloric acid reacting with it. Consequently, more excess hydrochloric acid remains, necessitating more sodium hydroxide to neutralize it.
| Experiment | Mass of Toothpaste (g) | Volume of NaOH (mL) | Percentage of CaCO3 in Toothpaste |
|---|---|---|---|
| 1 | 0.1 | 15.0 | 21.5% |
| 2 | 0.2 | 13.5 | 17.0% |
| Average | 19.2% |
The results show that the percentage of calcium carbonate in toothpaste is approximately 19.2%. This value is close to the expected percentage of 20%. The slight deviation may be attributed to human errors, such as the subjective judgment of the titration endpoint. Additionally, the dilution of the indicator due to the addition of deionized water during rinsing could have affected the color change, making it less noticeable.
It is crucial for the percentage of calcium carbonate in toothpaste to be around 20% to effectively remove dental plaque and food particles without causing enamel thinning or tooth sensitivity. The experiment's success in achieving a result close to the expected value indicates that the toothpaste composition meets these criteria.
In conclusion, the experiment determined that the percentage of calcium carbonate in toothpaste is approximately 19.2%. The smaller the amount of toothpaste used, the greater the volume of sodium hydroxide required to neutralize excess hydrochloric acid. While there was a slight difference between the percentages obtained in the two trials (21.5% and 17.0%), the average value of 19.2% is close to the expected 20%. This experiment demonstrates the importance of maintaining the correct percentage of calcium carbonate in toothpaste to ensure its effectiveness and safety for dental care.
For future experiments, it is essential to minimize potential sources of error, such as ensuring a more precise titration endpoint and avoiding excessive dilution of the indicator. Additionally, conducting multiple trials and calculating averages should be continued to improve the accuracy of results. Further research can explore the effects of varying calcium carbonate percentages in toothpaste on its abrasive and dental care properties.
Calcium Carbonate Analysis in Toothpaste. (2016, Aug 11). Retrieved from https://studymoose.com/document/pchem-formal-report
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