Calcium Carbonate (Caco3) Content In Toothpaste By

Synopsis

This experiment is the determination of Calcium Carbonate (CaCO3) content in toothpaste with the use of back titration while demonstrating quantitative transfer of solids and liquids. A accurately weighed quantity of toothpaste was dissolved in excess volumes of HCl. This solution is then titrated with NaOH to find the volume of the excess HCl. The volume of HCl reacted, which is found by substracting the volume of given HCl with the volume of excess HCl reacted, can be further manipulated with mole fractions to find the mass of CaCO3 and thus the CaCO3 content in toothpastes.

Results show that an average of 22.5% CaCO3 is found in toothpaste. Methyl Orange is noted to not be a suitable indicator for this experiment as the pH

In direct titrations, the number of moles of acid can be easily derived by simply manipulating with the values of acid and base given in the experiment.

In back titration, excessive volumes of acid are always added. Of which, only a certain quantity would be neutralised. The number of moles of acid is eventually derived from titrating this excess acid with a strong base and using mole fractions to calculate. The quantity of acid neutralised is obtained by subtracting the moles of acid given at the start of the experiment, with the moles of acid titrated.

Back titration is used for this experiment as Calcium Carbonate is volatile and is an insoluble salt. Therefore they cannot fully dilute with water. As it’s chemical and physical properties are non ideal for a Direct titration, Direct titration cannot be used to determine the Calcium Carbonate content in toothpaste. In Back titration, excess volumes of HCl acids are added to allow for titration with NaOH. Eventually, the moles of CaCO3 can be found via stoichiometric property of the two reactants, and the mass of CaCO3 can be determined.Thus, determining the CaCO3 content in

The average result obtained was 22.5% and is close to it’s literal value. This experiment had also proven to have shown effective transfer of solids and liquids as values of 1st and 2nd results, namely 22% and 23% respectively, were similar thereby showing consistency in results.

Phenolphthalein indicator was proven to be more suitable as an indicator as compared to Methyl Orange in this experiment. This is because Phenolphthalein the pH values of HCl involved in this experiment were in range of the pH values that bring about colour change in the Phenolphthalein indicators. (Approximate pH ranges for color change: 8.0-9.8) Low pH values are preferred for Methyl Orange. (Approximate pH ranges for color change: 3.1-4.4)

To sum up, back titration is a effective way for the determination of Calcium Carbonate as experimental results were close to it’s true and accepted value of 20%.

References

Antoine.frostburg.edu, (2014). Acid-Base Indicators. [online] Available at: http://antoine.frostburg.edu/chem/senese/101/acidbase/indicators.shtml [Accessed 12 Dec.