You need to produce a buffer solution that has a pH of 5.38. You already have a

Question

You need to produce a buffer solution that has a pH of 5.38. You already have a solution that contains 10. mmol (millimoles) of acetic acid. How many millimoles of acetate (the conjugate base of acetic acid) will you need to add to this solution? The pKa of acetic acid is 4.74. Express your answer numerically in millimoles.
Thanks!! You need to produce a buffer solution that has a pH of 5.38. You already have a solution that contains 10. mmol (millimoles) of acetic acid. How many millimoles of acetate (the conjugate base of acetic acid) will you need to add to this solution? The pKa of acetic acid is 4.74. Express your answer numerically in millimoles.
Thanks!!

Explanation / Answer

Since you are not making the acetate from the acetic acid present that means , using the Henderen/Haselbach equation
pH = pKa + log [base]/[acid] =
5.38 = 4.74 + log [10+X mmoles] /10mmol

0.64 = log [10+X]/X ;

4.36 = (10 +X) /10 43.6 = 10 + X
so the total acetate is 43.6 mmoles
Proof

pH = 4.74 + log 43.6/10 = 4.74 + log 4.36 = 4.74 + 0.64= 5.38

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