Question

Problem 17.21

Part A

Calculate the pH of a buffer that is 0.13 M in lactic acid and 0.11 M in sodium lactate.

Express your answer using two decimal places.

pH =

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Part B

Calculate the pH of a buffer formed by mixing 85 mL of 0.13 M lactic acid with 95 mL of 0.16 M sodium lactate.

Express your answer using two decimal places.

pH =

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Answer 1

The solution to both of these requires the use of the Henderson-Hasselbalch equation:  

pH = pKa + log([A^-]/[HA])

We also need the pKa of lactic acid (not given in the problem):

Acidity (pKa) 3.86

pH = pKa + log([A^-]/[HA])

pKa = 3.86
[A^-] = [sodium lactate] = 0.11 M .
[HA] = [lactic acid] = 0.13 M

pH = 3.79

Answer 2

https://answers.yahoo.com/question/index?qid=20140310133225AAjtg6U

do the same as in above link