1. To determine the percentage of calcium carbonate in eggshell
Chemistry Practical
Project work
To determine the percentage of
calcium carbonate in eggshell

2. Introduction Pesticides like DDT have been used extensively
The eggshell of the wild bird becomes weak and thin
The eggshell breaks before hatching

3. Principles Eggshell mainly consists of calcium carbonate
The percentage of calcium carbonate will be determined by acid/base titration
Direct titration of CaCO3 is very slow when the endpoint is near
Back titration will be performed

4. Principles The reactions take place are:
(1) 2HCl(aq) + CaCO3(s)  CaCl2(aq) + CO2(g)
(2) HCl(aq) + NaOH(aq)  H2O(l) + NaCl(aq)
(1) Number of moles and mass of CaCO3 can be calculated
(2) Percentage by mass of CaCO3 in eggshell can be calculated

5. Chemical Used 0.2075M of HCl 0.101188M of NaOH
A few drops of phenolphthalein indicator
95% of ethanol (CH3CH2OH)

6. Experimental Procedures

7. Experimental Procedures

8. Experimental Procedures

9. Experimental Procedures

10. Experimental Procedures

11. Experimental Procedures

12. Experimental Procedures

13. Experimental Procedures
2 decimal place!!
Repeat for three times!!
Another sample..

14. Experimental Results
Weight of the eggshell used: 0.2g

15. Experimental Results
Titration of eggshell (CaCO3) dissolved in excess HCl against NaOH (Brown Egg)
Trial 1 2 3
Final burette reading /cm3
2.30
1.30
0.00
21.00
Initial burette reading / cm3
20.60
19.50
18.10
39.00
Volume of NaOH used / cm3
18.30
18.20
18.00
Average volume of NaOH used:
= ( ) / 3
= 18.10cm3

16. Experimental Results
Titration of eggshell (CaCO3) dissolved in excess HCl against NaOH (White Egg)
Trial 1 2 3
Final burette reading /cm3
20.7
19.60
21.90
1.50
Initial burette reading / cm3
40.00
40.50
43.40
23.20
Volume of NaOH used / cm3
19.30
20.90
21.50
21.70
Average volume of NaOH used:
= ( ) / 3
= 21.37cm3

17. Observations
The phenolphthalein gave a pale pink colour from colorless at the end point

18. Observations
The HCl, NaOH and ethanol solution were colorless

19. Remarks The eggshell should be ground before drying
The eggshell was dried by the oven
Heating helped dissolving the eggshell
Ethanol helped HCl dissolve CaCO3
The phenolphthalein was used as an acid-to-base indicator
The solution was always diluted for reaction

20. Precautions The opening of container containing HCl should be covered
Safety goggles, gloves and coat should be worn
We should wash our hand after the experiment

21. Sources of errors The eggshell powder was not dissolved completely
Variation in visual judgment at the end point
Parallax error when reading the marks of the pipette or the burette
Instrumental errors of the electronic balance
Some HCl molecules might vaporize to the air
The reaction mixture was heated to boil

22. Calculations Percentage of CaCO3 in eggshell (Brown Egg)
No. of moles of HCl added to the mixture
= x 25 / 1000
= x 10-3 mol
Consider the equation:
HCl(aq) + NaOH(aq)  H2O(l) + NaCl(aq)
∵Ratio of no. of moles of HCl(aq) : that of NaOH(aq) = 1 : 1
∴No. of moles of HCl(aq) left
= x 18.1 / 1000
= x 10-3 mol

23. Calculations Percentage of CaCO3 in eggshell (Brown Egg)
∴No. of moles of HCl reacted
= x 10-3 – x 10-3
= x 10-3 mol
Consider the equation:
2HCl(aq) + CaCO3(s)  CaCl2(aq) + CO2(g)
∵Ratio of no. of moles of HCl(aq) : that of CaCO3(s) = 1 : 2
∴ No. of moles of CaCO3 in eggshell
= x 10-3 / 2
= x 10-3 mol

24. Calculations Mass of CaCO3 = 1.678 x 10-3 x ( 40.1 + 12 + 16 x 3 )
Percentage of CaCO3 in eggshell (Brown Egg)
Mass of CaCO3
= x 10-3 x ( x 3 )
= 0.168g
Percentage of CaCO3 in brown eggshell
= / 0.2 x 100%
= 84%

25. Calculations Percentage of CaCO3 in eggshell (White Egg)
No. of moles of HCl added to the mixture
= x 25 / 1000
= x 10-3 mol
Consider the equation:
HCl(aq) + NaOH(aq)  H2O(l) + NaCl(aq)
∵Ratio of no. of moles of HCl(aq) : that of NaOH(aq) = 1 : 1
∴No. of moles of HCl(aq) left
= x / 1000
= x 10-3 mol

26. Calculations Percentage of CaCO3 in eggshell (White Egg)
∴No. of moles of HCl reacted
= x 10-3 – x 10-3
= x 10-3 mol
Consider the equation:
2HCl(aq) + CaCO3(s)  CaCl2(aq) + CO2(g)
∵Ratio of no. of moles of HCl(aq) : that of CaCO3(s) = 1 : 2
∴ No. of moles of CaCO3 in eggshell
= x 10-3 / 2
= x 10-3 mol

27. Calculations Mass of CaCO3 = 1.5126 x 10-3 x ( 40.1 + 12 + 16 x 3 )
Percentage of CaCO3 in eggshell (White Egg)
Mass of CaCO3
= x 10-3 x ( x 3 )
= g
Percentage of CaCO3 in white eggshell
= / 0.2 x 100%
= 75.7%

28. Conclusion
The percentages of calcium carbonate in brown eggshell (Malaysia) is 84% and white eggshell (USA) is 75.7%.
The lower the percentage is, the more serious the pollution in the area is.
The percentages point out that pollution in Malaysia is more serious than that in USA.

29. Division of work Lam Chun Kit (Leader) Powerpoint creation
Lam Lung Chong
Data collection
Leung Fung Chi
Yip Shul Ching
Data analysis
Ma Cheuk Lung