Chemistry Question and Answers Essay

676 Words Apr 5th, 2014 3 Pages
1. What are the significant regions in the titration curve? Relate the characteristics of each region to the pH results obtained.

- There are four significant regions in each titration curve, namely the initial, pre-equivalence, equivalence, and post-equivalence points. These points are named according to its position relative to the equivalence point.
The equivalence point signifies the volume of titrant at which the solution becomes neutral. This is represented in the graph as the drastic change in pH, first with a sudden increase and a sudden decrease of pH.
At the initial point, no titrant has been added yet and the solution’s pH equates to the number of H+ ions originally present in the analyte.
At the
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Using this method, the amount of titrant used for weak acids would be the same as that used for strong acids since it is the number of protons or H+ ions, measured through the pH, which determines the equivalence point. With normal titrations of strong acids and bases, since H+ completely dissociates, similar concentrations with a weak acid and strong base titration would not be the same since weak acids do not dissociate completely. Another advantage of potentiometric titration is the fact that indicators are not used, therefore human error due to failure of recognition of color change may be avoided.

5. Discuss possible reasons behind the discrepancies (if any) in the experimental and theoretical pKa values.
- Human errors may have affected the results, such as miscalculations, overtitrations and failure of determination of the right pH value since the pH meter tends to fluctuate. Another source of error could be from the pH meter apparatus itself, particularly the electrodes since the classroom’s conditions are not perfect. The failure to rinse the electrodes may result to drastic changes as well. Another error may result from the failure in accuracy of the analytical balance since it has been used for several years prior.

6. What are the possible sources of errors and their effect on the calculated parameters? Rationalize.
- One of the members of the group accidentally touched the magnetic stirrer therefore contaminating the whole set-up. Since it cannot be

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