Experiment 9:Acidity Constants of Mande Prelab Practice Assignment 1. Donald Don

Question

Experiment 9:Acidity Constants of Mande Prelab Practice Assignment 1. Donald Donegood prepared a solution of mandelic acid by dissolving 1.504 grams in water and diluting to a final volume of 100.0 mL. He found the solution's pH to be 2.29. Fill in the following table and show how you obtained your results. co(M) H ]M) Ka 2. Next Donald wanted to prepare 100.0 mL a 1.25 M solution of acetic acid from a stock solution of 2.00 M acetic acid. How many mL of acetic acid should he pipet into a 100.0 mL volumetric flask before filling it to the line with water? ?? 7 0 % acidity how many of acetic acid are in 50.0

Explanation / Answer

1)

moles of mandelic acid = 1.504 / 152.15

= 9.885 x 10^-3 mol

final volume = 100.0 mL

concentration Co = 9.885 x 10^-3 / 0.1

= 0.09885

cocnetration Co = 0.09885 M

pH = 2.29

[H+] = 10^-2.29 = 5.13 x 10^-3 M

[H+] = 5.13 x 10^-3 M

[H+] = sqrt (Ka x C)

5.13 x 10^-3 = sqrt (Ka x 0.09885)

Ka = 2.66 x 10^-4

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