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Chemistry project
To determine the percentage ofcalcium carbonate in eggshell
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Content Introduction
Principle of this experiment Apparatus and equipments
Experiment procedures
Chemical used
Sample used Source of errors
Assumption made
Experimental results Calculations
Conclusion
Sources of references
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Introduction 1960's - 1970's USA used a pesticide, DDT extensively
Run-off from DDT entered our waterways andeventually into many of our wild birdlife.
DDT affected the population by weakening the
eggshells which would break before hatching.
An example of this devastation was the American BaldEagle whose population was as low as 400 matingpairs in the lower 48 states.
DDT has been banned in the USA and the Bald Eagle isno longer on the endangered species list. One method
of monitoring the strength of the egg is by determiningthe percentage of calcium carbonate in the eggshell.
This can be accomplished through an acid/basetitration method.
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Principle of the experiment
During this lab, the percentage of CaCO3 in an eggshell isdetermined by reacting the eggshell with hydrochloric acid. Theequation for this reaction is:
2HCl (aq) + CaCO3(s) Ca2+
(aq) + CO2 (g) + H2O (l) + 2Cl-
(aq)
This reaction cannot be used directly titrate with the CaCO3.Instead, an excess of hydrochloric acid is added to dissolve theeggshell, and the remaining acid is titrated with NaOH solution
to determine the amount of acid that did not react with theeggshell. The equation used to determine the amount of leftoveracid is:
HCl (aq) + NaOH (aq) H2O (l) + Na+ (aq) + Cl- (aq)
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In order to help the hydrochloric acid dissolve the CaCO3,
ethyl alcohol is added to the eggshell as a wetting agent.
Wetting agents are chemicals that increase the spreading and
penetrating properties of a liquid by lowering its surface
tensionthat is, the tendency of its molecules to adhere to
each other.
Although it is now banned in the United States, the
pesticide DDT has caused significant damage to theenvironment and its wildlife. Birds are especially affected
because the DDT weakens the shells of their eggs, which would
break before hatching. This caused certain bird species to
become endangered (i.e. the American bald eagle). One method
of monitoring the strength of the egg is by determining thepercentage of calcium carbonate in the eggshell.
The percentage of calcium carbonate indicate that the
strength of the eggshell and the strength of the eggshell show
how serious the pesticide damaged to the eggshell.
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Apparatus and equipments
250.00 cm3 beaker X4
glass rod X1
Filter funnel X1
Wash bottle X1
Electronic balance X1
Weighing bottle X1 250.00cm3 volumetric flask X2
25.00 cm3 pipette X2
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Conical flasks X2 Measuring cylinder X1
Bunsen burner X2
Heatproof mat X1
Burette X2
Wire gaze X2
Tripod X2
White tile X2
Mortar and pestle X2
Oven X1
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Chemical used
0.1M NaOH
0.2M HCl
Phenolphthalein
Ethanol
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Sample used
2 different eggs (1 white & 1 brown)
Malaysia
USA
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Procedures
1) The eggs was boiled and cooleddown.
2) The protein membrane wasremoved on the inside of theboiled eggshell.
3) The eggshell was washed withdistilled water
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5) The eggshell was then grounded into fine
powder by mortar and pestle.
(white egg) (brown egg)
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6) Dried inan oven for ten minutes.
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7) 0.2g of eggshell powder is weightedaccurately by using an electronic balance
and it was transferred to a conical flask.
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8) 25.00 cm3 of HCl was pipetted
to dissolve the eggshellpowder and 5 cm3 of ethanolwas also added in order to
help the HCl dissolve theCaCO39) Distilled water was added to
the flask until it reachedabout 50cm3. The flask wasswirled gently.
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10) The mixture was boiled for about 15
minutes (boiling away CO2) and thencooled down.
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15 minutes!!! Cool down!!10) Boil !!
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Experimental set-up
Burette
NaOH
stopcock25.00cm3 of HCl +
0.2g if egg shell powder
+ 5.00cm3
of ethanol +3 drops of
phenolphthalein +
about 20.00cm3 ofdistilled water
Conical flask
Burette stand
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11) The solution wasthen titrated withstandardized
NaOH.12) Repeat another
sample
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Experimental results
White egg:
Colourless pink
The colour change of the solution:
Brown egg:
Colourless pink
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Trial 1 2 3
15.20 20.00 18.30 13.10
0.00 0.00 0.00 0.00
15.20 20.00 18.30 13.10
Final burette reading/cm3
Initial burette reading/cm3
Volume of NaOH used/cm3
The titration result of brown egg:
Average volume of NaOH used:(20.00+18.30+13.10)/3=17.13cm3
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The titration result of white egg:
Trial 1 2 3
19.50 19.60 19.80 19.70
0.00 0.00 0.00 0.00
19.50 19.60 19.80 19.70
Final burette reading/cm3
Initial burette reading/cm3
Volume of NaOH used/cm3
Average volume of NaOH used:(19.60+19.80+19.70)/3=19.7cm3
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Calculations2HCl (aq) + CaCO3(s) Ca
2+ (aq) + CO2 (g) + H2O (l) + 2Cl- (aq)
HCl (aq) + NaOH (aq) H2O (l) + Na+
(aq) + Cl-
(aq)
Number of moles of NaOH used to react with HCl:
(17.13cm3 /1000) X0.1M = 1.713 X 10-3 mol
Since number of moles of NaOH = number of moles of HCl
= 1.713 X 10-3 mol
The initial no of moles of HCl: volume X molarity
= 25/1000 X0.2M = 5X10-3 mol
Number of moles of HCl used to react with CaCO3 :
(5X10-3 - 1.713 X 10-3) mol=3.287 X10-3 mol
For brown egg:
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Number of moles of CaCO3 reacted:
3.287X10- 3 /2
= 1.6435X10-3 mol
The weight of CaCO3:
1.6435X10-3g X100.1
=0.1645g
The % of CaCO3 in eggshell (brown) :
(0.1645/0.2) X100%
=82.25%
According to the equation, one mole of HCI required to
react with 2 moles of CaCO3,
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For white egg:
Number of moles of NaOH used to react with HCl:
(19.7/1000)X0.1 = 1.97X10-3mol
Since number of moles of NaOH = number of moles of HCl
= 1.97X10-3mol
The initial moles of HCl: volume X molarity
= 25/1000 X0.2M = 5X10-3 mol
Number of moles of HCl used to react with CaCO3 :
( 5X10-3 - 1.97X10-3) mol =3.03 X10-3 mol
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Number of moles of CaCO3 reacted:
3.03 X10-3/2
= 1.515X10-3 mol
The weight of CaCO3:
1.515X10-3g X100.1
=0.15165g
The % of CaCO3 in eggshell (white) :
(0.15165/0.2) X100%
= 78.83%
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Summary of Calculations
No. of moles of NaOH used to react with HCl/
mol
2.97X 10-3
No. of moles of HCl used to react with NaOH
/mol
2.97X 10-3
Initial moles of HCl / mol 1X10-2
No. of moles of HCl used to react with CaCO3
/mol
7.07 X10-3
No. of mols of CaCO3 reacted/ mol 3.535X10-3
The weight of CaCO3/ g 0.3535
The % of CaCO3in eggshell 70.07%
For Brown egg:
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For white egg:
No. of moles of NaOH used to react withHCl/ mol
1.97 X 10-3
No. of moles of HCl used to react withNaOH /mol
1.97 X 10-3
Initial moles of HCl / mol 5X10-3
No. of moles of HCl used to react withCaCO3 /mol
3.03 X10-3
No. of mols of CaCO3 reacted/ mol 1.515X10-3
The weight of CaCO3/ g 0.1517
The % of CaCO3in eggshell 75.82%
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Sources of errors
The eggshell powder did not dissolvecompletely
Variation in visual judgement at the end point
Instrumental errors of the electronic balance
The eggshell was not fully dried Some droplets of solution may still adhere on the beaker and the glass rod which
lead to the reduction in number of moles of excess HCl we should wash our hands
after the experiment
There was vaporization during boiling.
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Remarks During titration, control the stopcock of the burette with your
left hand. Swirl the conical flask with your right hand Use a conical flask to dissolved the eggshell since colourless
gas bubbles will be evolved. It is to prevent the solution fromjumping out .(CO2 is formed)
When dissolving the eggshell in a conical flask, use a stirrer tostir the solution well in order to make sure that the eggshell istotally dissolved
After pouring the solution mixture of eggshell and HCl into avolumetric flask, remember to rinse the stirrer and the conicalflask with distilled water and pour the washing to thevolumetric flask
After filling up the burette with NaOH, we should remember to
remove the filter funnel on the top of the burette Bubble in the burette should be removed before the initial
reading of the burette is read
we should swirl the conical flask after each addition. Distilledwater should be added to rinse the NaOH down the flask
Put a white tile under the conical flask for clearer observation
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Safety precautions
Dilute NaOH is corrosive
Do not touch chemicals with barehands
Safety goggles should be put on duringthe experiment
We should wash our hands after theexperiment
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Conclusion
By comparing the percentage of two eggs,
brown egg (Malaysia) has a higher
percentage than white egg (USA) indicate
brown egg has a higher strength than white
egg. It also show that eggs from USA have
a more serious problem of using DDT.
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Sources of references
http://www.chem.csustan.edu/chem1102/E
gg.htm
www.wikipedia.com
http://www.chem.csustan.edu/chem1102/Egg.htmhttp://www.chem.csustan.edu/chem1102/Egg.htmhttp://www.wikipedia.com/http://www.wikipedia.com/http://www.chem.csustan.edu/chem1102/Egg.htmhttp://www.chem.csustan.edu/chem1102/Egg.htm7/29/2019 Determination Of CaCO3 In the eggshell
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The end!
Thank you for your attention!ByeBye!