Back Titration Of Calcium Carbonate In Toothpaste

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1. Synopsis
The main aim of the experiment is to find out the percentage of calcium carbonate in toothpaste by using back titration since calcium carbonate is an insoluble salt and does not dissolve in water. Back titration is a reverse method of titration used to obtain unknown concentration of analyte. A roughly weighed quantity of toothpaste? calcium carbonate is dissolved in a known amount of hydrochloric acid and is then titrated against sodium hydroxide. An orange colour will be observed at the end point. This experiment is a success as two results obtained from the experiment were relatively close furthermore, an average of 21.50% of calcium carbonate obtained is close to the literature value of 20%.
2. Introduction
There are several
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The primary standard used are often acid or bases and can be titrated directly over the solution slowly to a known volume of another solution of unknown concentration until the reaction reaches its end point. However, if the substance to be analysed is volatile or an insoluble salt which in this experiment, calcium carbonate is, back titration is used instead of direct titration. Back titration will first be done by reacting an unknown concentration of insoluble or volatile substance with an excess amount of known concentration of acid or base. An excess amount of acid or base is preferred so as to fully dissolve the volatile substance and followed by back titrating the unreacted acid or base with a base or acid respectively. Therefore, for this experiment a back titration was carried out by using a weak base which is toothpaste with a strong acid which is Hydrochloric …show more content…
A direct titration can only be carried out when both acid and base are strong, strong base and a weak acid or a weak base and a strong acid. Moreover, the concentration of the unknown solution can be found directly. On the other hand, back titration is carried out when both acid and base are weak. Two reactions have to be carried out to find the concentration of the unknown solution. Therefore, back titration is used for this experiment as sodium hydroxide and hydrochloric acid are weak base and acid respectively. Therefore, the difference between a direct and a back titration ? of the bases and acid

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