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

Estimating the % purity of marble by back titration method

Extracts from this document...


Chemistry Lab - Conclusion and Evaluation Estimating the % purity of marble by back titration method Trial No. Percentage Purity of CaCO3 Uncertainty 1 90.37% �4.81% 2 95.11% �4.86% Average 92.74% �4.84% The values for the % purity of marble that I have calculated lie in a close range, however there is a significant difference, of 4.74% in the purity estimated between the 2 individual values. Nonetheless, the deviation is covered by the uncertainty of �4.84%. However, certain errors have occurred that have caused this deviation in the final results. REASONS FOR DEVIATION Random Errors 1. Loss of marble after weighing: After weighing out the marble, there is a small loss in mass in transferring the mass from the butter paper used for weighing as ...read more.


3. Air bubbles in pipette dispenser: For this experiment, due to the corrosive nature of the concentrated acid, a pipette dispenser was used to measure out the HCl. However there were some air bubbles that were trapped that cause an error in the volume of HCl that is not accounted for by the absolute uncertainty of the pipette. Systematic Errors 1. Unevenly crushed marble: The CaCO3 provided was not evenly crushed; some was still in larger chunks while the rest was finer granules. This non-uniformity in the texture of CaCO3 also creates a different surface area for the acid to react with and this can be the cause of the differing values of purity. ...read more.


2. Carefully using apparatus to avoid human errors: By practice and careful usage one can eliminate the errors caused by the air bubbles in the pipette, errors in transfer and parallax. 3. Marble should be crushed evenly: the CaCO3 should all be of the same texture so that the surface area is kept controlled and this will reduce the disparity in the purity values that have been caused by the differing surface areas. 4. Using another indicator that prevents uncertainty in the exact point of neutralization: If a solution like Universal Indicator is used then the exact point when the titration is complete can be easily identified and thus by eradicating this error, one can aim to reduce the disparity observed in the readings. ...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

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. Design Lab, HCl + Marble chips

    Average mass of CO2 = Trial 1 + Trial 2 + Trial 3 3 = (0.41 + 0.45 + 0.47) 3 = 0.44 g Uncertainty: (Highest value - Lowest value) 2 = (0.47 - 0.41) 2 = �0.03g Therefore, 0.44g �0.03g Average rate of reaction: Mass of CO2(g)

  2. alkali titration

    amount of oxalic acid present = 0.00097 mols �1.23% 4. What amount of oxalic acid was present in your 250 cm3 volumetric flask? Concentration of acid in 250mL is the same as the concentration of acid in 1L. Therefore the concentration of acid in 1 dm-3 of acid solution is

  1. Determination of the purity of commercial aspirin

    Evaluation: The errors mentioned above are presented here along with their improvements: Weaknesses Improvement Reading error existed when reading the volume of sodium hydroxide in the burette. My partner and I read the scale in turn, and then we take the average value.

  2. FInding the percentage purity of CACO3 in egg shell

    the volume of the alkali that will be required to neutralize the base. 1. Room temperature at which the experiment is performed There can be a difference in the concentration of the solution if the solution prepared and the experiment performed is at different temperatures .Hence an ideal way to

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