1. Law ManWai(09) Lai MeiLing(28) Mo WanI(32)
Chemistry Practical Project Work Determination of Calcium Carbonate in eggshell
Law ManWai(09) Lai MeiLing(28) Mo WanI(32)

2. 1 . Principle of experiment
Egg shell : calcium carbonate
Readily dissolve in acid, but not pure water
2HCl(aq)+CaCO3(s) Ca2+(aq)+CO2(g)+H2O(l)+2Cl-(aq)
Reaction rate is slow, cannot be titrate directly.
Back titration is used HCl(aq)+NaOH(aq) H2O(l)+Na+(aq)+Cl-(aq)
Amount of CaCO3 =the difference between amount of HCl initially added and the amount left over after the reaction

3. 2 . Experiment procedures
Clean & label a 150 ml beaker
Break the egg into a beaker. Remove the white and the yolk from the egg and dispose pf them down the drain.
Wash the shell with distilled water and carefully peel all the membrane from the inside of the shell. Dry it with a paper towel and put into a labeled beaker.

4. 2 . Experiment procedures
Dry the shell for about 10mins in a 120ºC oven.
Take out the eggshell from the oven and cool to room temp.. Weight the beaker wirth the eggshell and record this weight onto the data file. Determine the weigh of the eggshell.
Place the eggshell in a mortar and grind it into a powder with the pestle.

5. 2 . Experiment procedures
Accurately weigh 0.1g dried eggshell into each of 3 labeled 125ml conical flasks. Be certain the record of the mass of shell for each flask.
Add 5ml of alcohol to each flask. This acts as a wetting agent and helps the HCl dissolve the CaCO3.
Slowly pipette 10.00ml of 1.0M HCl in each flask. Swirl the flask to wet all of the solid. Any excess HCl should be disposed of in the sink by diluting with water.

6. 2 . Experiment procedures
Heat the solutions in the flasks for 5min because it need to remove CO2.
Rinse the walls of the flask with water from the wash bottle.
Add 3-4 drops of phenolphthalein (a-ka PHRL) to each flask.
Using a funnel, partly fill a clean burette with M NaOH solution to rinse it. Empty the burette into the sink. Fill the burette with the NaOHsolution

7. 2 . Experiment procedures
Run some solution out to remove all bubbles from the tip. Replenish the solution in the burette if necessary. Read and record the initial volume to+/-o.o1ml.
Titrate one sample to the first persistent pink colour. When it is closed to the end point the colour will fade slowly.

8. 2 . Experiment procedures
Add the remaining NaOH drop wise until the colour remains at least 30sec. Read and record the final volume to +/-0.01ml.
Repeat the titration for the other two samples.
Calculate the percent calcium carbonate in each sample and the mean value. Calculate the average deviation from the mean.
Wash the egg residue out of the conical flask with hot soapy water and a test tube brush.

9. 3 . Chemicals and concentration of solution used
Chemical used: 1M HCl 0.1MNaOH Ethanol Phenolphthalein distilled water
Sample used: Fresh Brown eggs (China) Fresh Leghan egg (From HK)

10. 4. Source of errors Not all the samples are dissolved
Not all the dissolved samples are transferred to the conical flask.
Variation in visual judgement at the end point.
Operative errors as the mixture in the volumetric flask was not well-shaken.
Titration run too fast and miss the exact end-point.

11. 5. Precaution
We should avoid contacting the NaOH(aq) and HCl(aq) as they are corrosive.
Add 5ml alcohol to each flask, it acts as a wetting agent and help the HCl dissolve the CaCO3.
Heat the solutions in the flasks for 5 minutes because it need to remove CO2.
6. Remark

12. 7 . Experimental result Average = 41.6ml Average = 40.4ml Trial 1st
Fresh Leghan egg (From HK)
Fresh Brown eggs (China)
Trial
1st
2nd
3rd
Initial volume(ml)
0.00
Final volume(ml)
37.00
41.10
39.90
44.40
NaOH used
Trial
1st
2nd
3rd
Initial volume(ml)
0.00
Final volume(ml)
40.00
41.10
40.10
40.50
NaOH used
Average = 41.6ml
Average = 40.4ml

13. 8. Calculation Fresh Leghan egg (From HK)
No. of mole of NaOH used= 0.2*41.6/ = mole =no. of mole of HCl remaining after the experiment.
initial no. of mole of HCl=1*10/1000
=0.01mole
No. of mole of HCl used by CaCO3=
= mole
No. of mole of CaCO3= /2= mole
Mass of CaCO3 = *( *3 )/0.1*100%= %

14. 8. Calculation Fresh Brown eggs (China)
No. of mole of NaOH used= 0.2*40.4/ = mole =no. of mole of HCl remaining after the experiment.
initial no. of mole of HCl=1*10/1000
=0.01mole
No. of mole of HCl used by CaCO3=
= mole
No. of mole of CaCO3= /2= mole
%Mass of CaCO3 = *( *3)/0.1*100%= %

15. Why Calcium Carbonate in egg shell varies??
9. Discussion
Fresh Brown eggs (China) : % of CaCO3
Fresh Leghan egg (From HK) : % of CaCO3
Why Calcium Carbonate in egg shell varies??

16. 6. Discussion DDT Dichlorodiphenyldichloroethylene
affected the environment affect the reproductive system, embryo development and baby growth.
affected the Eggshell Thinning interferes with certain reproductive enzymes in birds. affected the bird's embryo. disturbs Ca absorption, the content of Ca in shell may decrease.

17. The end of our presentation
Thank you for attention !!!