Introduction l Pesticides like DDT have been used
Introduction l Pesticides like DDT have been used extensively l The eggshell of the wild bird becomes weak and thin l The eggshell breaks before hatching
Principles Eggshell mainly consists of calcium carbonate l The percentage of calcium carbonate will be determined by acid/base titration l Direct titration of Ca. CO 3 is very slow when the endpoint is near l Back titration will be performed l
Principles l The reactions take place are: l (1) 2 HCl(aq) + Ca. CO 3(s) Ca. Cl 2(aq) + CO 2(g) l (2) HCl(aq) + Na. OH(aq) H 2 O(l) + Na. Cl(aq) l (1) Number of moles and mass of Ca. CO 3 can be calculated l (2) Percentage by mass of Ca. CO 3 in eggshell can be calculated
Chemical Used l 0. 2075 M of HCl l 0. 101188 M of Na. OH l A few drops of phenolphthalein indicator l 95% of ethanol (CH 3 CH 2 OH)
Experimental Procedures
Experimental Procedures
Experimental Procedures
Experimental Procedures
Experimental Procedures
Experimental Procedures
Experimental Procedures
Experimental Procedures l 2 decimal place!! l. Repeat for three times!! l. Another sample. .
Experimental Results l Weight of the eggshell used: 0. 2 g
Experimental Results l Titration of eggshell (Ca. CO 3) dissolved in excess HCl against Na. OH (Brown Egg) Trial 1 2 3 Final burette reading /cm 3 2. 30 1. 30 0. 00 21. 00 Initial burette reading / cm 3 20. 60 19. 50 18. 10 39. 00 Volume of Na. OH used / cm 3 18. 30 18. 20 18. 10 18. 00 Average volume of Na. OH used: l = (18. 20+18. 10+18. 00) / 3 l = 18. 10 cm 3 l
Experimental Results l Titration of eggshell (Ca. CO 3) dissolved in excess HCl against Na. OH (White Egg) Trial 1 2 3 Final burette reading /cm 3 20. 7 19. 60 21. 90 1. 50 Initial burette reading / cm 3 40. 00 40. 50 43. 40 23. 20 Volume of Na. OH used / cm 3 19. 30 20. 90 21. 50 21. 70 Average volume of Na. OH used: l = (20. 90+21. 50+21. 70) / 3 l = 21. 37 cm 3 l
Observations l The phenolphthalein gave a pale pink colour from colorless at the end point
Observations l The HCl, Na. OH and ethanol solution were colorless
Remarks l The eggshell should be ground before drying l The eggshell was dried by the oven l Heating helped dissolving the eggshell l Ethanol helped HCl dissolve Ca. CO 3 l The phenolphthalein was used as an acidto-base indicator l The solution was always diluted for reaction
Precautions l The opening of container containing HCl should be covered l Safety goggles, gloves and coat should be worn l We should wash our hand after the experiment
Sources of errors l l l 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
Calculations Percentage of Ca. CO 3 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) + Na. OH(aq) H 2 O(l) + Na. Cl(aq) ∵Ratio of no. of moles of HCl(aq) : that of Na. OH(aq) = 1 : 1 l ∴No. of moles of HCl(aq) left l = 0. 101188 x 18. 1 / 1000 l = 1. 8315 x 10 -3 mol l l l
Calculations Percentage of Ca. CO 3 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: 2 HCl(aq) + Ca. CO 3(s) Ca. Cl 2(aq) + CO 2(g) ∵Ratio of no. of moles of HCl(aq) : that of Ca. CO 3(s) = 1 : 2 l ∴ No. of moles of Ca. CO 3 in eggshell l = 3. 356 x 10 -3 / 2 l = 1. 678 x 10 -3 mol l l l
Calculations Percentage of Ca. CO 3 in eggshell (Brown Egg) l Mass of Ca. CO 3 l = 1. 678 x 10 -3 x ( 40. 1 + 12 + 16 x 3 ) l = 0. 168 g l Percentage of Ca. CO 3 in brown eggshell l = 0. 168 / 0. 2 x 100% l = 84%
Calculations Percentage of Ca. CO 3 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) + Na. OH(aq) H 2 O(l) + Na. Cl(aq) ∵Ratio of no. of moles of HCl(aq) : that of Na. OH(aq) = 1 : 1 l ∴No. of moles of HCl(aq) left l = 0. 101188 x 21. 37 / 1000 l = 2. 1624 x 10 -3 mol l l l
Calculations Percentage of Ca. CO 3 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: 2 HCl(aq) + Ca. CO 3(s) Ca. Cl 2(aq) + CO 2(g) ∵Ratio of no. of moles of HCl(aq) : that of Ca. CO 3(s) = 1 : 2 l ∴ No. of moles of Ca. CO 3 in eggshell l = 3. 0251 x 10 -3 / 2 l = 1. 5126 x 10 -3 mol l l l
Calculations Percentage of Ca. CO 3 in eggshell (White Egg) l Mass of Ca. CO 3 l = 1. 5126 x 10 -3 x ( 40. 1 + 12 + 16 x 3 ) l = 0. 1514 g l Percentage of Ca. CO 3 in white eggshell l = 0. 1514 / 0. 2 x 100% l = 75. 7%
Conclusion l The percentages of calcium carbonate in brown eggshell (Malaysia) is 84% and white eggshell (USA) is 75. 7%. l The lower the percentage is, the more serious the pollution in the area is. l The percentages point out that pollution in Malaysia is more serious than that in USA.
Division of work Lam Chun Kit (Leader) Powerpoint creation Lam Lung Chong Data collection Leung Fung Chi Powerpoint creation Yip Shul Ching Data analysis Ma Cheuk Lung Data collection
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