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Ib Eggshell Report

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Candidate's name: Eunika Orłowska
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Determining the amount of CaCO3 in eggshell of hen's egg

| Design | DCP | CE | Aspect 1 | | | | Aspect 2 | | | | Aspect 3 | | | |

Introduction: The back titration is a method used in determining the amount of excess of the reagent. The calcium carbonate is a substance which gives the eggshell stiffness.

Research question: What is the amount of calcium carbonate in the eggshell measured by back titration?

Table 1. Variables.

Type of variable | Variable | Unit | Dependent | Amount of calcium carbonate in eggshell | % by mass | …show more content…

The fact that the result has shown 100% of calcium carbonate in the eggshell may lay in the construction of eggshell which is biological "machine" to give hen's embryo the best possible environment for development. Apart from calcium carbonate, there are other components of eggshell, for example magnesium carbonate and calcium phosphate which also react with hydrochloric acid.

Reaction of calcium phosphate with hydrochloric acid:

Ca3(PO4)2 + 6HCl → 3CaCl2 + 2H3PO4

this reaction should't have influence on titration that much, because as a result there's the same number of hydrogen ions which can be neutralized, but the second reaction, of magnesium carbonate and hydrochloric acid:

MgCO3 + 2HCl → MgCl2 + CO2 + H2O

also takes HCl to it's reaction, decreases number of H+ ions and so suggests that more HCl reacted with calcium carbonate. This is the uncontrolled variable, the impurity of the eggshell, which affected the result.

Other factor, which may have had influence on the results is the human's imprecision. The used equipment was as accurate as possible in school laboratory, but still, the titration is made by hand and by eye, which may make mistakes although back titration is the best possible way in school laboratory to check the amount of particular components in mixtures. Other method, which would distinguish between

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