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To begin Part B: Buffered Acetic Acid vs. NaOH 30 mL of a buffered 0.25 M acetic acid solutionwas prepared. This was done by adding 1.021 g of solid sodium acetate trihydrate to a clean 100 mLbeaker. 15 mL of deionized H2O was added to the beaker along with 15 mL of 0.5 M acetic acid. The solution was then stirred. A 50 mL solution of 0.25 M NaOH was then prepared and stirred using 25 mL of deionized H2O and 25 mL of 0.5 M NaOH.The burette was then conditioned again with two 10 mL potions of deionized H2O and two 5 mL portions of the 0.25 M NaOH prepared earlier. The burette was then filled with the remaining 0.25 M NaOH up to the 0 mL mark and the volume was recorded. Below the prepared burette a beaker with 40 mL H2O, a stir bar, and 10 mL of the 0.25 M buffer was placed. The tip of the pH probe was then placed into the beaker solution and a new run was initiated by clicking collect. Fromhere the titration was begun by adding NaOH in 0.5 mL increments until the pH of the solution 2
changed dramatically. Once this occurred six 0.5 ML portions of NaOH were added. For each additions the volume and the pH was recorded and then finally the data collection was stopped, the waste reaction mixture was disposed of, and the pH probe was cleaned. To begin Part C: Buffered Acetic Acid vs. HCL a 50 mL 0.25 M HCl solution was prepared by adding 25 mL of deionized H2O to 25 mL 0.5 M HCL and stirring. The burette was then reconditioned using two 10 mL portions of deionized H2O and two portions of the 0.25 M HCl solution prepared earlier. The burette was then filled with the remaining 0.25 M HCl all the way up to the 0 mL mark. A beaker with a stir bar, 40 mL deionized H2O, and 10 mL of the 0.25 M buffer wasstirred and placed under the burette. The pH probe was then rinsed and placed inside the solution, before a new run was initiated and data collection began. 0 was recorded as the initial volume and HCl was added in 0.5 mL increments until the pH of the solution changed dramatically. Once this happened six 0.5 mL portions were added and the volume and pH after each addition were continued to be recorded. Data collection was then stopped, the reaction was disposed of, the pH probe was stored away, and the data collected from all titrations was saved. RESULTS & DISCUSSIONThe goal of this lab was to correctly perform normal titrations and titrations of buffers usinga pH probe, a 50 mL burette, and LoggerPro, to create a second derivative curve, and determine the equivalence point. Some other goals were also to determine the experimental pKaof acetic acid, calculate the corresponding value of Ka, and to determine the buffering capacity of the buffered acetic acid solution. After data analysis of Part A, Part B, and Part Cusing LoggerPro, the average pH at the half-equivalence point from the acetic acid titrations was able to be determined. It ended up being a pH of 5.353. Using the pH the pKawas determined using the knowledge that at the half equivalence point of titrating a weak acid like acetic acid with a strong base like sodium hydroxide, pH=pKa. So,