Titration of a Weak Acid

# Titration of a Weak Acid - Acid Base Titration Part 2 Name...

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Acid Base Titration Part 2 3/03/08 Name: Ron Walters Partner(s): John Alderman TA: Chad Teters Section 11 Monday 12-3

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Abstract- The purpose of this experiment was to show how polyprotic acids, acids which can donate more than one proton, will give off extra protons if you keep adding a base to the solution, giving more than one equivalence point. Then, using the pH value at half of the equivalence point, and doing some calculations, we can see that the pH is equal to the pKa value. In order to figure out what our equivalence points were, we used MeasureNet and a drop counter to see how much volume of base was needed to be added to the base in order to make the solution neutral. What we found from our experiments is that the molarity of the base we were using, NaOH was 0.09904 M, and the acid started out at 0.0835 M, but then after being titrated once went down to 0.0795 M, or an average of 0.0815 M. The Ka values we got were 4.0 x - 10 3 for the first titration, and 1.26 x - 10 7 for the second titration. These were roughly -46.6% and 103.2%, respectively, off from known literature values. Theory- In order to figure out why the pKa value was equal to the pH value at the half equivalence point, we needed to use the Henderson-Hasselbalch equation which states that the pH is equal to the pKa plus the log of the conjugate base divided by the acid, or
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Titration of a Weak Acid - Acid Base Titration Part 2 Name...

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