Determination Of CaCO3 In the eggshell

7/29/2019 Determination Of CaCO3 In the eggshell

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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.htm


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The end!

Thank you for your attention!ByeBye!

Determination Of CaCO3 In the eggshell

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