Part of The Student Room Group

  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

FInding the percentage purity of CACO3 in egg shell

Extracts from this document...

Introduction

Aim Egg shell is hard and cracks easily when beaten because of the constituent of CaCO3.Our main aim will be to determine the purity or the percentage composition of CaCO3 in the egg shell by using the technique of back titration. The egg shell is just a representation of any substance containing CaCO3 in their constitution; this method could be used to find the percentage purity of marble, limestone, sea shell etc. Identification of Variables Independent variable 1. Purity of CaCO3 in the egg shell Dependent Variable 1. Volume of Hcl Controlled Variable 1. Concentration of Hcl The concentration of Hcl that is going to be used must be calculated for the experiment for show results. I took 4.931 g of egg shell which is 0.04931 moles. We will be following the procedure of back titration in this experiment since CaCO3is insoluble in water/reacts slowly with acid. Thus the first procedure of back titration is to react the substance with excess of acid , which means that we have to take a slightly high concentration of a preferred acid , in this experiment we have taken 2M of Hcl acid. ...read more.

Middle

16. Now pour the solution of egg shell and acid from the beaker in to the glass funnel carefully. 17. The solution is being filtered , it will take time. 18. The solution will not however add up to 250cm3 volume, so we need to add distilled water into the volumetric flask. Make sure that the water that is added stays under the filter paper level so as that it is being filtered. 19. After the solution has reached the 250cm3 , take a stirrer bar drop it in the volumetric flask , put the flask on the stirrer and let the solution stir for 2 hours. 20. Now take a pipette, make sure that the pipette is clean. 21. Rinse the pipette 22. Take a conical flask of 250cm3 and rinse it. 23. Using the pipette transfer the solution into the conical flask. 24. Take a burette and rinse it with NaOH , the desired alkali. 25. Put the plastic funnel on top of the beaker and carefully pour the alkali into the beaker. 26. Make sure that the meniscus is just above the zero mark. ...read more.

Conclusion

Back titration is a titration done in reverse; instead of titrating the original sample, a known excess of standard reagent is added to the solution, and the excess is titrated. A back titration is useful if the endpoint of the reverse titration is easier to identify than the endpoint of the normal titration, as with precipitation reactions. Back titrations are also useful if the reaction between the analyte and the titrate is very slow, or when the analyte is in a non-soluble solid. First measured mass of egg shell was taken and it was reacted with excess of HCl acid in a beaker. The solution was then taken and the volume was increased to 250cm3.Then using a pipette 25cm3 volume of the solution was taken and was poured into a volumetric flask and it was titrated against a known concentration of NaOH.This was repeated 7 times and the mean titre was found to be 21.11cm3. After finding the titre calculations were done to find the mass of CaCO3 present in the egg shell. The egg shell weighed 4.931 g ± 0.001 and was found to contain 4.750 g ± 0.1653 g CaCO3 . The % purity of the egg shell containing CaCO3 was found by using the give formula :- (Mass of CaCO3/Mass of egg shell) x 100 which gave 96.32% purity. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our International Baccalaureate Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

or


Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related International Baccalaureate Chemistry essays

  1. A comparison of various proprieary antacids

    needed to neutralize excess Hydrochloric acid(25 cm3, 0.5 M), after addition of an Eno sachet, for three trials. Trial Number 1 2 3 Final Volume of NaOH, cm3 �0.05 cm3 23.20 20.50 20.60 Initial Volume of NaOH, cm3 �0.05 cm3 0.00 0.00 0.00 Volume of NaOH �0.1 cm3 23.20 20.50

  2. Estimating the % purity of marble by back titration method

    Excess NaOH added in titration: While titrating the HCl and the HCl + CaCO3 solutions the usage of the phenolphthalein indicator causes an error in the amount of alkali added as the titration is only stopped once the colour changes to a pale pink, this firstly is a very

  1. Enthalpy Change Design Lab (6/6)How does changing the initial temperature (19C, 25C, 35C, and ...

    no limiting reactant during the investigation (as can also be verified by inspection when looking at the balanced equation for the reaction, displayed earlier). 3. The volume of both 1.00 mol dm-3 HCl(aq) and 1.00 mol dm-3 KOH(aq) solutions must be held constant throughout the course of the investigation, across all variations in temperature, and in all trials.

  2. Period 3 Chlorides. Aim: To study the chlorides of period 3 elements and ...

    magnesium chloride both have a small change (showing the physical process of dissolving), while aluminium chloride has a large temperature change (showing the chemical process of hydrolysis). And if we take a look at the pH change for each of them, we can see that when aluminium chloride was added to water, the pH decreased from 7 to 2.

  1. Calculate % of caco3 in white egg shell

    Using a graduated pipette add 20.0cm3 of 1.00moldm-3 of hydrochloric acid slowly any swirl the flask to prevent any small amount from escaping from the flask with the carbon dioxide that is produced. 2. Once the reaction is completed add about 20 cm3 of distilled water and transfer all

  2. Chemistry Titration Acid Base Lab

    On the other hand, sodium hydroxide contains sodium acetate which raises the pH considerably of the vinegar as it is fairly basic. Therefore, the equivalence point will be greater than seven and more specifically approximate to 9. All of the indicators that were used did not have a pH range above 9 except for phenolphthalein.

  1. Measuring the fatty acid percentage of the reused sunflower oil after numerous times of ...

    So when I started to read some news at the newspaper about the oils that companies use in frying, I started to question my meals and wanted to learn the reality about the potato frying which I eat everyday with my thousands of friends at school.

  2. Research question: how to convert NaOH to NaCl by two different routes , and ...

    0.36 % Number of moles (NaOH) Since n = Un. for the mass of NaOH = 0.1g Un. for the volume of water = 5x10-4 dm3 Calculating âH : = m (H2O) × c (H2O) × âT = -50.0× 4.18 × (35.0 -20.0) = -3135 J Since the number of moles used is the same, there

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work