Experiment 18 Buffer Solutions - Experiment 18 Buffer...

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Experiment 18 Buffer Solutions Roseanne Hylton Lab Instructor: Colin Henck Date of Lab: 3/28/19 Objective: The objective of this experiment is for students to find the pKa of acetic acid by multiple
methods and to determine if an acetic acid/sodium acetate solution is able to resist changes in pH. Hypothesis: In this experiment, it is expected that the pKa value of acetic acid is 4.75. In the experiment, the value will be experimentally calculating through two different methods. In the first method, the value of pKa of Acetic Acid will be determined by pH. This case involves using the formula for Ka and then converting it to pKa using the formula pKa = -logKa. We are able to do this because the concentration of hydronium hydronium and acetate in the Ka equation and these values are given to us by the pH since pH is also equivalent to [H3O+]= 10E-pH. In the second method, the pKa value of acetic acid is determined by making a buffer solution. In this case, a specific solution can be made such that the pH is equal to the pKa and you can simple measure the pH and have the pKa. Variables: In this experiment, the concentration of the acetic acid solution is the independent variable. The Ka/pKa values are the dependent variables. Experimental Procedure: Determining the concentration of Acetic Acid 1. Make a 150 mL solution of approximately 0.1 M NaOH by diluting the 5.0 M NaOH available in the lab. ( How to do this: Add 3 mL of 5.0 M NaOH and 147 mL of water in a clean, dry and LABELED 250 Erlenmeyer flask) 2. Next, the approximately 0.1 M NaOH