Titration Experiment 4, Chem 201

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See the pre-lab report on page 15 of my laboratory notebook for an outline of the general procedure. The unknown acid number was 6553, and the concentration of NaOH used in the experiment was .09912 M. Also, three drops of phenolphthalein indicator were added to the initial titration and the titration curve.


Initial Titration: * Volume of NaOH added at the endpoint was 29.8 mL

Titration Curve: * Volume of NaOH added at the endpoint was 29.0 mL


Acid concentration from first titration was .118M
Ka from initial pH was 1.08x10^-5
Acid concentration from titration curve was .115M

Titration | Volume of NaOH (mL) | pH | (base)/(acid) | pKa | Ka | 1/4 | 7.25 | 4.1 | 1/3 | 4.577 | 2.65x10^-5 | 1/2 | 14.5 | 4.6 | 1 | 4.6 | 2.55x10^-5 | 3/4 | 21.8 | 5.19 | 3 | 4.713 | 1.94x10^-5 | Average: | | | | 4.663 | 2.18x10^-15 |


The purpose of the experiment was to titrate a weak acid of unknown concentration with a strong base, NaOH, and then utilizing an initial titration and titration curve to determine that acid concentration and Ka. After performing the initial titration of the acid concentration, we calculated it to be 0.118 M, with a Ka of 1.08x10^-5. On the other hand, when we performed the titration curve, it calculated an acid concentration of 0.115 M and a Ka of 2.18x10^-5.
The results I obtained seemed reasonable since the acid concentration we acquired from both the initial titration and titration curve yielded a 0.003 difference in the amounts. This is due to the fact that the equivalence point for the initial titration was 29.8 mL, a similar amount with the titration curve of 29.0 mL. Both of these derived measurements demonstrate great precision since the values were close to each other, only a 0.8…...

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