Law ManWai(09) Lai MeiLing(28) Mo WanI(32) Chemistry Practical Project Work 2006-2007 Determination of Calcium Carbonate in eggshell Law ManWai(09) Lai MeiLing(28) Mo WanI(32)

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

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.

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.

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.

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 0.20204M NaOH solution to rinse it. Empty the burette into the sink. Fill the burette with the NaOHsolution

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.

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.

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)

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.

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

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

8. Calculation Fresh Leghan egg (From HK) No. of mole of NaOH used= 0.2*41.6/1000 =0.00832mole =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=0.01-0.00832 =0.00168mole No. of mole of CaCO3=0.00168/2=0.00084mole Mass of CaCO3 =0.00084*(40.1+12+16*3 )/0.1*100%= 84.084%

8. Calculation Fresh Brown eggs (China) No. of mole of NaOH used= 0.2*40.4/1000 =0.00808mole =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=0.01-0.00808 =0.00192mole No. of mole of CaCO3=0.00192/2=0.00096mole %Mass of CaCO3 =0.00096*(40.1+12+16*3)/0.1*100%= 96.096%

Why Calcium Carbonate in egg shell varies?? 9. Discussion Fresh Brown eggs (China) : 96.096% of CaCO3 Fresh Leghan egg (From HK) : 84.084% of CaCO3 Why Calcium Carbonate in egg shell varies??

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.

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