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08-09 Chemistry Report. Determine the calcium carbonate content of a sample of an egg shell. Members : Ho chi nam Tong wing kwan Chan siu sing Chan sing yeung Lee cheung fat. Introduction.

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08 09 chemistry report

08-09 Chemistry Report

Determine the calcium carbonate content of a sample of an egg shell

Members : Ho chi nam Tong wing kwan Chan siu sing Chan sing yeung Lee cheung fat

introduction
Introduction
  • The pesticide DDT has caused significant damage to the environment 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 the percentage of calcium carbonate in eggshell
principle
Principle
  • During this experiment,the percentage of CaCO3 in an eggshell is determined by reacting the eggshell with hydrochloric acid.
  • 2HCl(aq)+CaCO3(s)→Ca2+(aq)+CO2(g)+H2O(l)+2Cl-(aq)
back titration
Back titration
  • This reaction cannot be used directly to titrate the CaCO3 because it is dissolved in water.Thus ,we must use back titration.
  • Back titration is an analytical chemistry technique that allows the user to find the concentration of a reactant of unknown concentration by reacting it with an excess volume of another reactant of known concentration.
slide5
The resulting mixture is then titrated back, taking into account the molarity of the excess that was added.
  • Through to find out the molarity of resulting mixture,we can calculate the abundant of an unknown sample
slide6
In this experiment,excess of standard hydrochloric acid is added to dissolve the eggshell.
  • Ethyl alcohol is added to eggshell as a wetting agent to help the hydrochloric acid dissolve the CaCO3.
  • Wetting agents are chemicals that increase the spreading and penetrating properties of a liquid by lowering its surface tension – that is, the tendency of its molecules to adhere to each other.
slide7
The remaining acid is titrated with NaOH solution.
  • determine the amount of acid that did not react with the eggshellHCl(aq)+NaOH(aq)→H2O(l)+Na+(aq)+Cl-(aq)
  • Through to find out the amount of acid ,we can calculate the abundant of CaCO3.
experimental apparatus
Wash bottle x1

Conical flask x4

Mortar and Pestle x1

Filter funnel x1

Electronic balance x1

50.00ml Burette x1

White tile x1

25.00ml pipette

250.00ml beaker x2

Oven x1

Bunsen burner x2

Tripod x2

250.00ml volumetric flask x2

Experimental apparatus

Experimental apparatus

slide9

Experimental Chemical

  • Phenolphthalein
  • 0.101188M NaOH
  • 0.2175M HCl
  • Enthanol
  • Distilled water
  • Paper towel
  • Egg shell x2 (import form USA and Malaysia respectively)
procedure
Procedure

Preparing fine egg shell powder:

  • Eggs were put into boiling water for 5 minutes.
  • Eggshells of 2 eggs were washed with distilled water.
  • Eggshells of 2 eggs were obtained by break the eggs shell.
slide11
The inside membrane was removed.
  • The eggshell of 2 eggs was put into oven for 15 minutes.
  • The eggshell powder of 2 eggs were ground by using mortar and pestle.
preparation
Preparation
  • 0.20g of dried eggshells powder was weighed into each of 4 conical flask accurately.
  • 25.00cm3 of 0.2175M HCl solution was pipetted into each flask.
  • 5.00cm3 of ethanol was added to each flask.
  • The flasks were swirled to wet all of the solid .Any excess HCl should be disposed in the sink by diluting with water.
slide13
The solutions in the flasks were heated until they began to boil and allow to cool .The walls of the flasks were rinsed with distilled water from the wash bottle.
  • 3 drops of phenolphthalein was added to each flask.
slide14

7. A funnel was used to partly fill a clean burette with NaOH solution to rinse it.

  • 8. The burette was filled with NaOH solution by using a funnel, and some solution were run out to remove all bubbles from the tip.
  • 9. The initial volume was recorded.
slide15
10. Titrate the first sample to get a reference.

11. Titrate other three samples and record the results.

12. Calculate the percentage of calcium carbonate in each sample and the mean value.

13. Calculate the average deviation from the mean.

results
Results

Table showing the titration result of Malaysia egg shell :

Table showing the titration result of U.S.A egg shell :

calculations

Calculations

the initial moles of HCl = 0.2175M x 25cm3/1000cm3

= 5.4375 x 10-3 mol

HCl (aq) + NaOH (aq)→NaCL (aq) + H2O (l)

1 mole of HCl (aq) react with 1 mole of NaOH (aq)

the moles of HCl react with NaOH = the moles of NaOH used

=0.101188 x 24.1cm3/1000cm3

=2.4386308 x 10-3 mol

slide18

The moles of HCL react with CaCO3 = the Initial moles of HCl – the moles of HCl reacted with NaOH

= 5.1875 x 10-3mol – 2.4386308 x 10-3mol

=2.9988692 x 10-3mol

slide19

CaCO3 (s) + 2HCl (aq) →CaCl (aq) + H2O (l) + CO2 (g)

1 mole of CaCO3 react with 2 moles HCl

The moles of CaCO3 = 2.9988692 x 10-3mol / 2

= 1.4994346 x 10-3 mol

Percentage of CaCO3 in eggshell = 1.4994346 x 10-3mol x(40.1+12+16x3)g-mol/0.2g x 100

= 75.05%

slide20
the initial moles of HCl = 0.2175M x 25cm3/1000cm3

= 5.4375 x 10-3 mol

HCl (aq) + NaOH (aq)→NaCL (aq) + H2O (l)

  • 1 mole of HCl (aq) react with 1 mole of NaOH (aq)
  • the moles of HCl react with NaOH = the moles of NaOH used

=0.101188 x 29.8cm3/1000cm3

=3.015164 x 10-3 mol

slide21
The moles of HCL react with CaCO3 = the Initial moles of HCl – the moles of HCl reacted with NaOH = 5.4375 x 10-3 x 10-3mol –3.015164 x 10-3mol

=2.4220976 x 10-3mol

slide22
CaCO3 (s) + 2HCl (aq) →CaCl (aq) + H2O (l) + CO2 (g)
  • 1 mole of CaCO3 react with 2 moles HCl
  • The moles of CaCO3 = 2.4220976 x 10-3mol / 2 = 1.2110488 x 10-3 mol
  • Percentage of CaCO3 in eggshell =1.2110488 x 10-3 mol x(40.1+12+16x3)g-mol/0.2g x 100

=60.61%

observations
Observations
  • Bubbles appeared when dissolving egg shell powder by HCl(aq).
  • Eggshell powder could not completely dissolve in HCl.
  • The sodium hydroxide solution was colourless.
  • When the sodium hydroxide solution was added to the mixture of eggshell and hydrochloride, the mixture turned pink.
remarks
Remarks
  • Ethanol must be added before the boiling of mixture of eggshell and hydrochloride.
  • The ethanol should be stored in a closed vessel and was pipette only when it was used.
  • When the mixture heated to 80oC,the titration was started immediately.
  • Shark flask continuously during the titration.
  • Make sure that the eggshell powder was dry.
  • The conical flask should be heated by air bath because the mixture contain ethanol which is flammable.
source of error
Source of error
  • Variation in visual judgement at the end point.
  • Eggshell powder could not dissolve completely in HCl.
  • The inside membrane was not completely removed.
  • The mixture was not heated enough.
  • Although after through rinsing,not all the eggshell powder is transferred to the volumetric flask.
precautions
Precautions
  • The hydrochloride acid and Sodium hydroxide solution are corrosiveness.
  • During the heating, the safety goggles must be weared.
  • Label the containers of each solution because they are colorless solution.
  • We should wash our hands after the experiment.
conclusion

Conclusion

Though the experiment,the egg of Malaysia was found that the percentage of CaCO3 was 75.05%.The egg of U.S.A. was found that the percentage of CaCO3 was 60.61%.The egg of Malaysia contain more CaCO3 than the egg of U.S.A.

It reflect that the pollution of DDT is more serious in U.S.A