Back titration: a technique which can be used to determine the concentration of calcium carbonate in a sample. First, a known excess of an acid is added to the sample, which reacts with all the calcium carbonate present, forming calcium ions, water, and carbon dioxide. After the reaction is complete, the excess acid is titrated with a base of known concentration, and the volume of base required is used to calculate the amount of unreacted acid, which corresponds to the amount of calcium carbonate in the sample.
Hydrochloric acid will be added to the eggshell samples to determine the amount of calcium carbonate because it reacts completely, forming soluble products, facilitating straightforward quantification, and is a readily available and safe laboratory reagent.
An experimental procedure would be to crush the eggshell into powder. Mix it with an acid for a complete reaction. To quantify the calcium carbonate content, the excess hydrochloric acid will be titrated with a sodium hydroxide solution, with the endpoint of the titration determined using an pH indicator. The volume of sodium hydroxide required for neutralization will enable the calculation of the amount of calcium carbonate.
Possible limitations in determining calcium carbonate content in eggshells include incomplete reactions, impurities, titration errors, varying eggshell compositions, equipment precision, environmental factors, reagent purity, and sampling issues.
Indicators
-
Phenolphthalein will be the indicator used for this titration because it undergoes a dramatic and easily distinguishable colour change during acid-base titrations. It transitions from colourless to a vibrant pink near the equivalence point. This distinct and sharp transition allows for precise endpoint detection.
-
-