Chemistry Project.docx

Candidate’s Name: Bibi Fareada Khan, Aaliya Blackman, Brittney Barrington Shane France, Dominic Alleyne Candidate No: 090046 School: St. Rose’s High School School Code: 090046 Teacher’s Name: Miss Chester Territory: Guyana

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Statement of problem A gardener noticed that his crops were susceptible to root disease, stunted growth and discolored leaves, which were all effects of calcium deficiency. He decided to add egg shells to the soil to reduce this problem. However, he was indecisive when choosing the egg shells because he wanted to select the appropriate egg shell to supply the plants with maximum calcium for better growth. His grandmother told him brown egg shell contains a larger amount of calcium carbonate than white egg, while his brother told him both contains the same amount of calcium carbonate. Plan and design an experiment to investigate the calcium carbonate percentage in white and brown egg shells.

Title: Back Titration

Hypothesis Brown egg shells have a higher percentage of calcium carbonate than white egg shells. And will provide the plants with maximum supply of calcium.

Aim: To determine whether brown egg shell has a higher percentage of calcium carbonate than white egg shell.

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Background Information Calcium carbonate, more commonly known as calcitic lime or garden lime, has long been a staple in garden, field, and lawn management. There are four major benefits of adding calcium carbonate to the soil. These include: correcting soil pH, increasing the efficacy of other nutrients, adding calcium and reducing toxicity of metals in the soil. Calcium carbonate is an excellent product for raising the pH of soil. Most plants do best in soils with a pH between 5.5 and 6.5 (Maximum Yield, 2019). Calcium carbonate can be broadcast over and incorporated into soils in need of a dose of alkalinity. Also, calcium carbonate is a great source of calcium (Ca). Calcium is an important nutrient that strengthens a plant’s cellular walls and is vital in new cell development. Also, one of the many unseen benefits of using calcium carbonate, as it relates to its ability to adjust soil pH, is its role in making nutrients available to plants. All of the nutrients that a plant needs may be present in a soil, but they may be unavailable to plants (Nutrient Lockout, 2010). If the pH is not conducive for the plant to easily “grab a hold” of then majority of nutrients that a plant needs are most available to plants at the aforementioned 5.5 to 6.5 pH range. In order to investigate the concentration of calcium carbonate in egg shells, a back titration is mandatory to conduct. Back titration is a quantitative chemical analysis where the concentration of an analyte is determined by reacting the egg shell with 50ml of 1.0 moldm-3 volume of Hydrochloric acid. The solution is then made up in a 250 ml volumetric flask and then portions of 20 ml of the made of solution is titrated against 0.1 moldm-3 of Sodium Hydroxide. In this way, the analyte original concentration is determined. Some factors that affects this experiment include;

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o Determination of the end point; the student conducting the experiment may be uncertain about the colour change when the reaction is completely neutralized. Thus affecting the volume reading leading to inaccuracy. o The presence impurities in the egg shells. These may be reactive species, which may react with the chemicals leading to inaccurate results.

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Variables Controlled Variable o

The concentration of Hydrochloric acid used

o

The concentration of Sodium Hydroxide used

o

The Volume of HCl used to dissolve the egg shell

o

The mass of egg shell used.

o

The volume of water used to dilute the solution

o

The indicator used

o

The volume of mixture (HCl and egg shell) used

Independent Variable o

The brown egg shells

o

The white egg shells

Dependent Variable o

The volume of Sodium Hydroxide used.

o

Percentage calcium carbonate present in the egg shell.

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Apparatus o Funnel [1] o Beaker [3] o Pipette [3] o Dropper [3] o Electronic balance [1] o Volumetric flask [2] o Burette [2] o Wash bottle [1] o Mortar and pestle [1] o Conical flasks [8]

Reagents o Phenolphthalein o 1.0 M Hydrochloric Acid o 0.1 M Sodium Hydroxide

Materials o Tissue o White Egg [2] o Brown Egg [2]

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burette: containing the sodium hydroxide

retord stand

stop cock

conical flask containing the titre.

THE DIAGRAM ABOVE SHOWS THE APPARATUS SETUP THAT WILL BE USED TO INVESTIGATE CALCIUM CARBONATE CONCENTRATION IN EGG SHELLS.

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Methodology 1. Gather the materials, reagents and apparatus listed. 2. Obtain four brown and four white eggs. 3. Wash and boil the eggs for ten minutes. 4. Peel the eggs and ensure to obtain the shell without the membrane. 5. Dry the egg shell. 6. Grind the brown egg shell with a mortar in a pestle. 7. Weigh 1.0 grams of the egg shell. 8. Measure 50ml of 1.0 moldm-3 hydrochloric acid and transfer it to a beaker. 9. Add the weighed egg shell to the acid and heat it gently. 10.After effervescence stops, transfer the solution to a 250ml volumetric flask and make up to the mark with distilled water.

11.Pipette 20 ml of the solution into four conical flasks labeling rough, trial 1, 2 and 3. 12.Add two drops of phenolphthalein indicator to each flask. 13.Fill a beaker with about 100 mL of 0.100 M sodium hydroxide. Using a funnel, add the solution to a clean burette to rinse it. Empty the burette into the sink. Fill the burette with the sodium hydroxide solution just above the top mark. Run some solution out to remove and record the volume reading.

14.Titrate the NaOH against the rough, while swirling the conical flask. 15.At the sight of the persistent pink color add the remaining NaOH dropwise until the colour remains for at least 30 sec.

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16. Read and record the final volume to ±0.01 mL. 17.Repeat the titration for trials 1, 2 and 3. 18. Repeat steps 3 to 17 using the white egg shell. 19.Tabulate all volume readings recorded. 20. Then calculate the percent calcium carbonate in each sample.

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Expected Results Table 1 White Egg Shell BURETTE VOLUME READINGS

TRIALS ROUGH

[cm3]

1

2

3

INITIAL READING

a

B

c

d

FINAL READING

b

C

d

e

VOLUME OF TITRE

[b-a]

[c-b]

[d-c]

[e-d]

A

B

C

D

THE TABLE ABOVE SHOWS THE EXPECTED INITIAL READING, FINAL READING AND VOLUME OF TITRE FOR THE ROUGH, TRIALS 1,2 AND 3 WHEN THE SODIUM HYDROXIDE WILL BE TIRTRATED AGAINST THE WHITE EGG SHELL.

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Expected Calculations:

For white egg shells Average Volume of NaOH will be used: (B + C + D) = Q/3 = R cm3 1. Calculating the number of moles of NaOH that will react with HCl Mol of NaOH = Avg. volume of NaOH * Concentration of NaOH Rdm3/1000 * 0.1 moldm3 = S mol 2. Calculating the number of moles of HCl that will react with the NaOH HCl (aq) +NaOH (aq) →H2O (l) + NaCl (aq) Mol of HCl = Smol (since 1 mol of NaOH will react with 1 mol HCl) No. of Moles of HCl in 20ml = Smol x 250/20 =Tmol 3. Calculating the number of moles of HCl that will be initially added (original no. of mol): Moles of HCl = volume of HCl * concentration of HCl Moles of HCl = 50dm3/1000 * 1.0moldm3 = 0.05 mol 4. Calculating the number of moles of HCl that will react with the CaCO3 0.05 mol –Tmol = Umol 5. Calculating the number of moles of Calcium carbonated that will react 2HCl (aq) + CaCO3(s) →CaCl2 (aq) + H2O (l) + CO2 (g) U mol/2 = Vmol (Since 2 mol of HCl will react with 1 mol CaCO3) 6. The molar mass of CaCO3 = (40 + 12 + 16 + 16 + 16) = 100g/mol The mass of CaCO3 = No. of mole of CaCO3 * Molar mass of CaCO3 = Vmol X100g = Wg The percentage of CaCO3 in eggshell (white) = Mass of CaCO3/ mass of shells * 100 = (W/1.0g * 100) =XCaCO3

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Table 2 Brown Egg Shell

BURETTE VOLUME READINGS

TRIALS ROUGH

[cm3]

1

2

3

INITIAL READING

F

G

h

i

FINAL READING

G

H

i

j

VOLUME OF TITRE

[g-f]

[h-g]

[i-h]

[j-i]

E

F

G

H

THE TABLE ABOVE SHOWS THE INITIAL READING, FINAL READING AND VOLUME OF TITRE FOR THE ROUGH, TRIALS 1,2 AND 3 WHEN THE SODIUM HYDROXIDE WILL BE TITRATED AGAINST THE BROWN EGG SHELL.

For the calculations, the steps above will be repeated using the values for the brown egg shell.

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Interpretation of Expected Results This experiment will deem useful in the determination of the Calcium Carbonate concentration in the two egg samples, since they’re poorly water soluble. Hence, the acid will be reacted in excess. Also, CaCO3 is weak base, so the determination of the endpoint using direct titration will be difficult. When NaOH will be added to the solution, that has the acid in excess, a colour changed from colourless to pink will be observed. This will indicate that all the excess HCl had reacted with the NaOH and the solution was a bit alkaline, accounting for the slight pink colour change. The more NaOH that will be used to react with the HCl and CaCO3 mixture, the less CaCO3 will be present in the egg shells. The hypothesis will be proven accurate if the brown egg shell solution requires a smaller volume of NaOH than the white egg shell solution to neutralize the reaction completely. Otherwise, if the brown egg shell solution requires a larger volume of NaOH than the white egg shell solution, the hypothesis will be proven inaccurate.

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Sources of Error o The burette being slanted will result in incorrect volume readings being taken, which will lead to inaccurate results.

o The apparatus not being dried before using will alter the concentration of the reagents leading to inaccuracy.

o Uncertainty of the endpoint will result in acid being added even when the reaction will be completely neutralized leading to inaccurate results.

o The egg membrane not being completely removed will lead to inaccurate results since it will react with the acid.

Limitation o The sensitivity of the scale leading to inaccurate mass of egg shell being weighed. o The size of the last few drops of NaOH added from the burette when the end point will be near, exceeding the endpoint.

o The presence of reactive impurities in the egg shell samples, will contribute to inaccurate results.

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Precautions o Ensure caution is taken when the acid will be pipetted. o Ensure the volume of distilled water that will be added to the volumetric flask doesn’t exceed the 250 mark when making up the solution as it will contribute to inaccuracy.

o Ensure the burette is upright when the volume readings will be recorded, since inaccurate volume readings will contribute to inaccuracy.

o Ensure all meniscus are read at EYE LEVEL to reduce parallax error. o Ensure to rinse all apparatus with distilled water followed by the substance it will be measuring to avoid contamination. o Ensure to remove the membrane from the egg shell completely, since it will react with the acid leading to inaccurate result.

Assumption It will be assumed that calcium carbonate will be the only specie that will react with the Hydrochloric acid during this experiment.

Conclusion It will be concluded that the hypothesis is proven accurate. That is the brown egg shell has a higher percentage of calcium carbonate and it will provide the plant with the maximum supply of calcium than the white egg shell.

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Title: Back Titration

Aim: To determine whether brown egg shell has a higher percentage of calcium carbonate than white egg shell.

Theory Calcium carbonate, more commonly known as calcitic lime or garden lime, has long been a staple in garden, field, and lawn management. There are four major benefits of adding calcium carbonate to the soil. These include: correcting soil pH, increasing the efficacy of other nutrients, adding calcium and reducing toxicity of metals in the soil. In order to investigate the concentration of calcium carbonate in egg shells, a back titration is mandatory to conduct. Back titration is a quantitative chemical analysis where the concentration of an analyte is determined by reacting the egg shell with 50ml of 1.0 moldm-3 volume of Hydrochloric acid. The solution is then made up in a 250 ml volumetric flask and then portions of 20 ml of the made of solution is titrated against 0.1 moldm-3 of Sodium Hydroxide. In this way, the analyte original concentration is determined. Some factors that affects this experiment include; o Determination of the end point; the student conducting the experiment may be uncertain about the colour change when the reaction is completely neutralized. Thus affecting the volume reading leading to inaccuracy. o The presence impurities in the egg shells. These may be reactive species, which may react with the chemicals leading to inaccurate results.

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Apparatus o Funnel [1] o Beaker [3] o Pipette [3] o Dropper [3] o Electronic balance [1] o Volumetric flask [2] o Burette [2] o Wash bottle [1] o Mortar and pestle [1] o Conical flasks [8]

Reagents o Phenolphthalein o 1.0 M Hydrochloric Acid o 0.1 M Sodium Hydroxide

Materials o White Egg [2] o Brown Egg [2]

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burette: containing the sodium hydroxide

retord stand

stop cock

conical flask containing the titre.

THE DIAGRAM ABOVE SHOWS THE APPARATUS SETUP USED TO INVESTIGATE CALCIUM CARBONATE CONCENTRATION IN EGG SHELLS.

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Method 1. The materials, reagents and apparatus listed were gathered. 2. Four brown and four white eggs were obtained. 3. The eggs were washed and boiled for ten minutes. 4. The eggs were then peeled, and it was ensured to obtain the shell without the membrane. 5. The egg shells were then dried. 6. The brown egg shell was then pounded with a mortar in a pestle. 7. 1.0 grams of the egg shell was weighed. 8. 50ml of 1.0 moldm-3 hydrochloric acid was measures and transferred into a beaker. 9. The weighed egg shell was added to the acid and heated gently. 10.After effervescence stopped, the solution was transferred to a 250ml volumetric flask and made up to the mark with distilled water.

11. Then 20 ml of the solution was pipetted into four conical flasks labeling rough, trial 1, 2 and 3.

12. Two drops of phenolphthalein indicator to was added each flasks. 13. A beaker was filled with about 100 mL of 0.100 M sodium hydroxide. A funnel was used to add the solution to a clean burette to rinse it. The burette was emptied into the sink and it was filled with the sodium hydroxide solution just above the top mark and the volume reading was recorded.

14. The NaOH was titrated against the rough, while swirling the conical flask.

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15.At the sight of the persistent pink color the remaining NaOH was added dropwise (or by half drops) until the colour remained for at least 30 sec.

16. The final volume to ±0.01 mL was read and recorded. 17. The titration was repeated for trials 1, 2 and 3. 18.Steps 3 to 17 was repeated using the white egg shell. 19. All volume readings recorded were then tabulated. 20.The percent calcium carbonate in each sample was then calculated.

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Results Table 3 White Egg Shell BURETTE VOLUME READINGS

TRIALS ROUGH

[cm3]

1

2

3

0.0

0.0

0.0

0.0

FINAL READING

29.7

29.3

29.3

29.2

VOLUME OF TITRE

29.7

29.3

29.3

29.2

INITIAL READING

THE TABLE ABOVE SHOWS THE INITIAL READING, FINAL READING AND VOLUME OF TITRE FOR THE ROUGH, TRIALS 1,2 AND 3 WHEN THE SODIUM HYDROXIDE WAS TITRATED AGAINST THE WHITE EGG SHELL.

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Calculations:

For white egg shells Average Volume of NaOH used: (29.3 + 29.3 + 29.2) =87.8/3 = 29.3cm3 1. Calculating the number of moles of NaOH used to react with HCl Mol of NaOH = Avg. volume of NaOH * Concentration of NaOH 29.3dm3/1000 * 0.1 moldm3 = 0.00293 mol 2. Calculating the moles of HCl that reacted with the NaOH HCl (aq) +NaOH (aq) →H2O (l) + NaCl (aq) Mol of HCl = 0.00293 mol (since 1 mol of NaOH reacts with 1 mol HCl) No. of Moles of HCl in 20ml = 0.00293mol x 250/20 =0.036625 mol 3. Calculating the number of moles of HCl initially added (original no. of mol): Moles of HCl = volume of HCl * concentration of HCl Moles of HCl = 50dm3/1000 * 1.0moldm3 = 0.05 mol 4. Calculating the number of moles of HCl that reacted with the CaCO3 0.05 mol – 0.036625 mol = 0.013375mol 5. Calculating the number of moles of Calcium carbonated that reacted 2HCl (aq) + CaCO3(s) →CaCl2 (aq) + H2O (l) + CO2 (g) 0.013375 mol/2 = 0.0066875 mol (Since 2 mol of HCl reacts with 1 mol CaCO3) 6. The molar mass of CaCO3 = (40 + 12 + 16 + 16 + 16) = 100g/mol The mass of CaCO3 = No. of mole of CaCO3 * Molar mass of CaCO3 = 0.0066875 mol X100g = 0.66875g The percentage of CaCO3 in eggshell (white) = Mass of CaCO3/ mass of shells * 100 = (0.66875/1.0g * 100) =67 CaCO3 %

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Table 4 Brown Egg Shell BURETTE VOLUME READINGS

TRIALS ROUGH

[cm3]

1

2

3

0.0

0.0

0.0

0.0

FINAL READING

29.9

29.0

29.0

28.9

VOLUME OF TITRE

29.9

29.0

29.0

28.9

INITIAL READING

THE TABLE ABOVE SHOWS THE INITIAL READING, FINAL READING AND VOLUME OF TITRE FOR THE ROUGH, TRIALS 1,2 AND 3 WHEN THE SODIUM HYDROXIDE WAS TITRATED AGAINST THE BROWN EGG SHELL.

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Calculations: For brown egg shells Average Volume of NaOH used: (29.0 + 29.0 + 28.9) = 86.9/3 = 28.97cm3 1. Calculating the number of moles of NaOH used to react with HCl Mol of NaOH = volume of NaOH * concentration of NaOH 28.97dm3/1000 * 0.1 moldm3 = 0.00289 mol 2. Calculating the moles of HCl that reacted with this HCl (aq) +NaOH (aq) →H2O (l) + NaCl (aq) Mol of HCl = 0.00289 mol (since 1 mol of NaOH reacts with 1 mol HCl) No. of mole in 20 ml of HCl = ( 0.00289 * 250/20 ) = 0.036213 3. Calculating the number of moles of HCl initially added: Moles of HCl = volume of HCl * concentration of HCl Moles of HCl = 50dm3/1000 * 1.0moldm3 = 0.05 mol 4. Calculating the number of moles of HCl that reacted with the CaCO3 0.05 mol – 0.036213 mol = 0.013788 mol 5. Calculating the number of moles of Calcium carbonated that reacted 2HCl (aq) + CaCO3(s) →CaCl2 (aq) + H2O (l) + CO2 (g) 0.013788mol/2 = 0.006894 mol (Since 2 mol of HCl reacts with 1 mol CaCO3) 6. The molar mass of CaCO3 = (40 + 12 + 16 + 16 + 16) = 100g/mol The mass of CaCO3 = No. of mole of CaCO3 * Molar mass of CaCO3 = 0.006894 mol X100g = 0.6894g The percentage of CaCO3 in eggshell (white) = Mass of CaCO3/ mass of shells * 100 = (0.6894g/1.0g * 100)

= 69 CaCO3%

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Discussion The aim of this experiment conducted was to determine the percentage of calcium carbonate in egg shells. For this, back titration was deemed useful since egg shells are poorly water soluble. Also, the calcium carbonate present is a weak base, which would make the determination of the endpoint very difficult if direct titration method was used. Firstly, the egg shell was dissolved in excess HCl. Then the solution was diluted and 25cm3 of the madeup solution was titrated against 0.1 moldm-3 NaOH. A colour changed from colourless to pink was observed. This indicated that all the excess HCl had reacted with the NaOH and the solution was a bit alkaline, accounting for the slight pink colour change.

Based on the calculations, the number of moles of HCl in the 20cm3 of acid used was calculated to be 0.00293 mol in the white egg shell and 0.00289 mol for the brown egg shells. The average volume of NaOH was calculated to be 28.97 cm3 (0.02897 dm3) for the brown egg shell and 29.3 cm3 (0.0293 dm3) for the white egg shells. The average volume of NaOH was substituted into the equation number of moles= concentration*Average volume, to calculate the number of moles of NaOH, 0.00293 mol for the white egg shell and 0.002897 mol for the brown egg shell. The number of mol of HCl that reacted with the NaOH in the titration was found to be 0.00293mol for the white egg shell and 0.002897mol for the brown egg shell using the mole ratio. The number of moles of HCl that reacted with CaCO3 in each egg shell was found by subtracting the number of moles of HCl that reacted with the NaOH from the total number of moles of HCl in 20cm3. It was found to be 0.013375 mol for the white egg shell and 0.0137875 mol for the brown egg shell. This was found by using the mole ratio between HCl and CaCO3. The mass of CaCO3 in each egg shell was then calculated using the formula; mass = molar mass * number of

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moles, in which the mass of CaCO3 in white egg shell was found to be 0.66875g and 0.689375g for the brown egg shell. From the calculations, it was observed that the more NaOH used to react with the HCl and CaCO3 mixture, the less CaCO3 was present in the egg shells. Overall, the results of the experiment were precise and accurate. Multiple trials were performed, so precision was enhanced. The percent mass of CaCO3 in the white egg was found to be 66.9 %CaCO3 and for the brown egg shell it was 68.9% CaCO3.

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Sources of Error o The burette was slanted when the volume readings were taken. Hence, inaccurate burette which contributed to the inaccurate results.

o The apparatus was not dried before using, which altered the concentration of the reagents, contributing to inaccuracy.

o Uncertainty of the endpoint, this resulted in the acid being added even when the reaction was completely neutralized leading to in accurate results.

o The membrane was not fully removed from the egg shell. This reacted with the acid, leading to altered results.

o The egg shell didn’t completely react with the HCL because it was not crushed finely, which resulted in inaccurate results.

Limitation o The sensitivity of the scale leading to inaccurate mass of egg shell that was weighed. o The size of the last few drops of NaOH added from the burette when the end point was near exceeding the endpoint.

o The presences reactive impurities in the egg shell samples contributed to the overall percentage being a bit off.

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Precautions o Caution was taken when pipetting the acid. o Caution was taken when the distilled water was added to the volumetric flask, so that the water didn’t exceed the 250 mark when the solution was made up.

o All meniscus was read at EYE LEVEL, in order to reduce parallax error. o All apparatus was rinsed with distilled water followed by the substance it measures to avoid contamination.

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Reflection This experiment is beneficial to the researchers since knowledge was gained on how to use the various apparatus and how to conduct a back titration. After the completion of this project, the researchers noted that the white egg shell contained 67 percentage of CaCO3, while the brown egg shell contained 69 percentage of CaCO3. This was a difference of two percent. However, the researchers was expecting a higher CaCO3 content for each egg shell. Since previous researchers stated the composition of egg shells are approximately 90-95 percentage of CaCO3 and the remaining 5 percentage being magnesium, phosphorous iron, etc. This huge difference of the CaCO3 can be accounted by laboratory misconducts, not removing the egg membrane completely from the egg shell, and the presence of disturbances while using the scale, which resulted in inaccurate massed being obtained. Thus, affecting the results. Also, the egg shell was not crushed finely, in which it didn’t react completely with the acid. The researchers recommends to leave the HCl and egg shell overnight in order to ensure that the reaction was completed. However, with all that being said, this experiment is also deemed useful for the society and environment since the farmers will now be abe to choose the appropriate egg shells. That is the brown egg shells, which has a higher calcium carbonate content. This means, the famer will be able provide his crops with a maximum supply of calcium which will enhance the growth and yielding of the crops and reduces the susceptibility of root diseases. Also, the farmers will be able to get fresher looking crops at the market selling, since the appropriate egg shell will be chosen, which reduces the discolouration of leafy crops. And in this way, they will be able to get maximum sale on the market.

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Lastly, the researcher would recommend investigating which type of egg shell has a higher iron, magnesium and phosphate content, since this will also be useful to gardeners.

Conclusion In conclusion, it was found that brown egg shells contain 69 percentage of CaCO3 while White egg shell contains 67 percentage of CaCO3.

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