Estimating the % purity of marble by back titration method

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Chemistry Lab – Conclusion and Evaluation

                                                                                   

Estimating the % purity of marble by back titration method

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

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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 a small quantity of the fine powdered marble sticks to the butter paper and does not react with the HCl at all. Also, while transferring the crushed CaCO3 some particles could have also been blown away by the wind. Thus the disparity in the masses used could account for the different values obtained.
  2. HCl left in the pipette: being a manual instrument, there is no ...

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