2. Determine the volume of 0.1M NaOH consumed during the titration. Record the answer. 3. Calculate the Molarity of the Acetic Acid in the vinegar samples. Record the answer. 4. Calculate the pK a of acetic acid from the midpoint data using the HendersonHasselbach equations in the Background section. 5. Find the average calculated molarity, percent by mass concentration, and pK a for acetic acid based on the provided data. Data Table 3: Titration of Vinegar by Sodium Hydroxide Vinegar Sample 1 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
8 Volume of NaOH Consumed 17.23 ml 17.31ml 17.39ml Calculated Molarity of Acetic Acid in the Vinegar Sample 0.87M 0.87M 0.87M Volume NaOH Consumed at Midpoint Reading 8.66 ml 8.7 ml Moles of NaOH Consumed at Midpoint Reading [A–] 0.04398M 0.044M Moles of Acetic Acid Remaining at Midpoint [HA] .01759M 0.174M Calculated p K a 4.289 4.316 Average calculated molarity of acetic acid ____________0.87M_______________ Average acetic acid concentration expressed in percent by mass ___17.4ml________ 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%__________
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- Fall '15