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Calculate % of caco3 in white egg shell

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´╗┐Anant Sultania Teacher?s Instruction Determine the composition of the eggshell. Aim To find the percentage purity of Calcium Carbonate in an egg shell Variables Independent variables: mass of calcium carbonate in eggshell The mass of calcium carbonate in the egg shell will be constant as the shell is taken form one egg itself. Dependent variables: number of moles of hydrochloric acid used The number of moles of that reacts with the calcium carbonate will vary according to the mass of calcium carbonate that is present in eggshell. Control variable: concentration of sodium hydroxide The concentration of is used for titration is kept constant this will give the accurate measurements of the amount of that did not react with the calcium carbonate Apparatus 1. Mortar and Pestle 2. Standard Lab Balance 3. Hot Plates 4. 200ml beaker 5. Graduated measuring cylinder (10ml, 100ml) 6. Pipette 7. Burette 8. Conical Flask Reagents Used 1. Eggshell 2. 3. 4. Phenolphthalein Procedure 1. Carefully wash the shell of an egg to remove any dirt and organic matter attached to it. ...read more.


At this point stop the flow of sodium hydroxide. 7. Note down the reading that is shown on the burette. Data collection And Processing The following table shows the data that was collected: S. No. Volume of NaOH used./±0.5cm3 1 20.5 2 21.1 3 20.3 4 20.4 5 20.9 6 20.3 The average of sodium hydroxide that was used to neutralize the hydrochloric acid is: The error in the average value is: The process of back titration can be used to find out the mass of The two reactions that occur during the process are: We can see from the above equation that of reacts with of Finding the number of moles of sodium hydroxide: Therefore: The total amount of that was taken is: The error here is as the least count on a measuring cylinder is and the final error is Now the amount of that reacted with can be calculated by: of reacts with of therefore of will react with The value is Now moving on to calculate the percentage purity of in eggshell: The error in the percentage purity is: This error ...read more.


This again results in an increase in the error in the experiment and thus this is the flaw that is present in the procedure. When the reacted solution of the salt and the acid is diluted the concentration of the unreacted acid decreases and the error is increased even further. The most significant error in the percentage purity was caused by the measuring cylinder. As every time a measure of of was taken it was not accurate and this resulted in the varation in the amount of that was neutralized each time. The improvements that can be added to the experiments will be: 1. Using a dropper to measure an accurate amount of the solution so there is a minimum of variation in the calculated values. 2. Titrating about of solution as it is easier to isolate form the total solution and at the same time the results will improve and there will be a reduction in the uncertainty of the experiment. 3. The titration should be carried our very carefully so that excess of is not used and thus the result will be more accurate. With these improvements one should attain a more accurate result. ________________ | Page ...read more.

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