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Chemistry Practical

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Chemistry Practical. Project work 2008-2009. To determine the percentage of . calcium carbonate in eggshell. Introduction. Pesticides like DDT have been used extensively The eggshell of the wild bird becomes weak and thin The eggshell breaks before hatching. Principles.

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Chemistry Practical
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  1. Chemistry Practical Project work 2008-2009 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) • Average volume of NaOH used: • = (18.20+18.10+18.00) / 3 • = 18.10cm3

  16. Experimental Results • Titration of eggshell (CaCO3) dissolved in excess HCl against NaOH (White Egg) • Average volume of NaOH used: • = (20.90+21.50+21.70) / 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 • = 0.2075 x 25 / 1000 • = 5.1875 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 • = 0.101188 x 18.1 / 1000 • = 1.8315 x 10-3 mol

  23. Calculations Percentage of CaCO3 in eggshell (Brown Egg) • ∴No. of moles of HCl reacted • = 5.1875 x 10-3 – 1.8315 x 10-3 • = 3.356 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 • = 3.356 x 10-3 / 2 • = 1.678 x 10-3 mol

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

  25. Calculations Percentage of CaCO3 in eggshell (White Egg) • No. of moles of HCl added to the mixture • = 0.2075 x 25 / 1000 • = 5.1875 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 • = 0.101188 x 21.37 / 1000 • = 2.1624 x 10-3 mol

  26. Calculations Percentage of CaCO3 in eggshell (White Egg) • ∴No. of moles of HCl reacted • = 5.1875 x 10-3 – 2.1624 x 10-3 • = 3.0251 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 • = 3.0251 x 10-3 / 2 • = 1.5126 x 10-3 mol

  27. Calculations Percentage of CaCO3 in eggshell (White Egg) • Mass of CaCO3 • = 1.5126 x 10-3 x ( 40.1 + 12 + 16 x 3 ) • = 0.1514g • Percentage of CaCO3 in white eggshell • = 0.1514 / 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