Vinegar sample 2 vinegar sample 3 initial ph reading

Vinegar
Sample 2
Vinegar
Sample 3
Initial pH Reading pH = 3.211 pH = 3.102 pH = 3.105
Initial Buret Reading 2.89 mL 3.00 mL 1.61 mL
Midpoint pH Reading pH = 4.895 pH = 4.687
Midpoint Buret Reading 12.92 mL 9.50 mL
Final pH Reading pH = 8.238 pH = 8.531 pH = 8.934
Final Buret Reading 20.12 mL 20.31 mL 19.00 mL
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Name of Sample Vinegar
Vinegar
Sample 1
Vinegar
Sample 2
Vinegar
Sample 3
Volume of NaOH Dispensed 17.23 mL 17.31 mL 17.39 mL
Calculated Molarity of Acetic
Acid in the Vinegar Sample
0.87 0.87 0.87
Volume NaOH Dispensed at
Midpoint Reading
8.6 mL 8.7 mL
Moles of NaOH Consumed at
Midpoint Reading
[A–]
0.044 M 0.044 M
Moles of Acetic Acid
Remaining at Midpoint [HA]
0.176 M 0.174 M
Calculated p K
a
4.29 4.32
Average calculated molarity of acetic acid:
0.87 M
Average acetic acid concentration expressed in percent by mass:
17.4 mL
Average value of p K
a
of acetic acid based on provided experimental data:
4.3%
Percent error for p K
a
of acetic acid: 7.9%
© 2016 Carolina Biological Supply Company

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2. Given the following experimental data, calculate the molarity and the p K
a
of the acid analyte (HA) in the titration, if the balance neutralization
reaction is:
HA + NaOH à NaA + H
2
O.
A pH reading of 3.65 was obtained when 13.0 mL of 0.413 M NaOH was
added to the 25.0 mL analyte.
The endpoint was achieved when 31.25 mL of NaOH had been added.
Photos
Photo 1
Insert the photo of the 25-mL Erlenmeyer flask after the addition of
phenolphthalein from Activity 1, step 6.
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Photo 2
Insert the photo of the 25-mL Erlenmeyer flask at the endpoint of the
titration from Activity 1, step 13.
© 2016 Carolina Biological Supply Company