Determination of Calcium Carbonate in Eggshells

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Determination of Calcium Carbonate in Eggshells

Purpose The purpose of this lab is to find out how much calcium carbonate is in an eggshell.

Results .454g CaCO2 2.86mL NaOH 107% CaCO2 .451g CaCO2 3.00mL NaOH

Observations When we poured the HCl into the eggshell it bubbled
Clumps of white eggshell left When we dropped the correct amount of NaOH it turned fluorescent pink because of the phenolphthalein indicator

Calculations First Trial Second Trial Third Trial
2.86mL NaOH∗ 0.1 M NaOH 1000 mL ∗ 1 mol HCl 1 mol NaOH =2.86∗ 10 −4 10 mL HCl∗ 1 M HCl 1000 mL =0.01 mol HCl−2.86∗ 10 −4 mol HCl= mol HCl used mol HCl∗ 1mol Ca mol HCl ∗ 1 mol CaC O 3 1 mol Ca 2+ = mol CaCO 3 ∗ g CaC O 3 1 mol CaC O 3 = g CaC O g CaC O 3 ∗100=107% Second Trial 2.35mL NaOH∗ 0.1 M NaOH 1000 mL ∗ 1 mol HCl 1 mol NaOH =2.35∗ 10 −4 10 mL HCl∗ 1 M HCl 1000 mL =0.01 mol HCl−2.35∗ 10 −4 mol HCl= mol HCl used mol HCl∗ 1mol Ca mol HCl ∗ 1 mol CaC O 3 1 mol Ca 2+ = mol CaCO 3 ∗ g CaC O 3 1 mol CaC O 3 = g CaC O g CaC O 3 ∗100=108% Third Trial 3.00mL NaOH∗ 0.1 M NaOH 1000 mL ∗ 1 mol HCl 1 mol NaOH =3.00∗ 10 −4 10 mL HCl∗ 1 M HCl 1000 mL =0.01 mol HCl−3.00∗ 10 −4 mol HCl= mol HCl used mol HCl∗ 1mol Ca mol HCl ∗ 1 mol CaC O 3 1 mol Ca 2+ = mol CaCO 3 ∗ g CaC O 3 1 mol CaC O 3 = g CaC O g CaC O 3 ∗100=107%

Conclusion We suck at doing experiments.

Conclusion Continued.. Just kidding~!
We were able to find out how much calcium carbonate is in an eggshell through the process of volumetric analysis. Applying significant figures to our calculations would skew our results from 107% and 108% to 100%. That still doesn’t make sense because calcium carbonate isn’t the only component of eggshells. Also, we had excess eggshell after adding the HCl which would have skewed our results in the opposite direction than they were skewed. So our results aren’t too reliable. One theorized issue might have been the molarity of the HCl. We repeated the calculations using 0.8 M instead of the labeled 1 M and got a percent calcium carbonate of 85% which makes sense. The theoretical results after research were found to be between 77% and 95% calcium carbonate in the eggshell. Cool!