khangExperiment7.doc

khangExperiment7.doc - Chemistry 241L Spring 2012...

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Chemistry 241L Spring 2012 EXPERIMENT 7 NAME: TD Khang DATE: 2/15/12 SECTION: 410 TA: Emilie Mainz The worksheet has been adapted from: Buckley, P. T. J. Chem. Ed. 2001 , 78, 1384. 1. Pre-Lab Questions. Graded before start of lab. ______ / 10 pts 2. What is your assigned pH? Make sure to write this in your lab notebook as well. Assigned pH = 4.85 3. You and your partner will prepare a buffer solution to this pH. From ______ / 5 pts the assortment of reagents you have available to you in the lab hood, which two will you use to create this buffer and why ? The available reagents are listed in Table 1 of your lab manual. There is a table of pKa values (Table 2) that are also available in your lab manual. We will be using Acetic Acid and Sodium Acetate Trihydrate as our reagents to create the buffer. Acetic Acid is the HA and Sodium Acetate Trihydrate is the Aˉ. We will be using Acetic Acid because the pKa, listed as 4.756 in Table 2 of Experiment 7, is closest to the assigned pH of 4.85 and it will lead to the maximum buffer capacity. When pH = pKa, the buffer capacity is at its maximum. In order for pH to equal pKa, the [Aˉ] must equal the [HA] in the Henderson Hasselbalch Equation which would lead to Log (1) = 0. When the concentrations of weak acid and conjugate base are equal, the buffer will react to either additional base or acid. It is very hard to find a reactant that
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This note was uploaded on 02/29/2012 for the course BIOC 107 taught by Professor Staff during the Spring '12 term at UNC.

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khangExperiment7.doc - Chemistry 241L Spring 2012...

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