A. Phosphate Buffer 1. Prepare 100 mL of a 0.01 M phosphate buffer, pH 7.70, from stock solutions of 0.1 M K2HPO4and 0.2 M KH2PO4. (pKa for the weak acid = 7.20). a. Use the Henderson-Hasselbalch equation to calculate the volume of each stock solution needed. pH = RKa + log [conjugate base] / [weak acid] b. Check your calculations with other students. See the instructor if there is uncertainty. c. Make the solution and check the pH of a portion of your buffer solution using the pH meter.

A. Phosphate Buffer 1. Prepare 100 mL of a 0.01 M phosphate buffer, pH 7.70, from stock solutions of 0.1 M K2HPO4and 0.2 M KH2PO4. (pKa for the weak acid = 7.20). a. Use the Henderson-Hasselbalch equation to calculate the volume of each stock solution needed. pH = RKa + log [conjugate base] / [weak acid] b. Check your calculations with other students. See the instructor if there is uncertainty. c. Make the solution and check the pH of a portion of your buffer solution using the pH meter.

Chemistry: Principles and Reactions

8th Edition

ISBN:9781305079373

Author:William L. Masterton, Cecile N. Hurley

Publisher:William L. Masterton, Cecile N. Hurley

Chapter14: Equilibria In Acid-base Solutions

Section: Chapter Questions

Problem 74QAP: Fifty cm3 of 1.000 M nitrous acid is titrated with 0.850 M NaOH. What is the pH of the solution (a)...

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Can someone please explain why and how the step 1 was done? What was its purpose? Why was only the pKa2 value was used in the second step 2? I don't understand shortcuts and I would appreciate it if it's explained step by step. This was the solution to my previous question in which I asked: What is the pH of a buffer prepared by mixing 100 mL 0.050 mM NaH2PO4 and 25 mL 0.075 mM Na2HPO4? (pKa1=2.2; pKa2= 7.21; pKa3=12.7)
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