You need to produce a buffer solution that has a pH of 5.02. You already have a

Question

You need to produce a buffer solution that has a pH of 5.02. 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.

i'm keep getting an wrong answer. 79.43 what i got for my answer. Please do show the calculations. i have only one attempt left on mastering chemistry so please do give me the right answer and i will rate you if i'll get the correct answer. Thax:)

Explanation / Answer

Use the Henderson-Hasselbalch equation

pH=pKa + log[A-/HA] *log is base 10, A- is conj base, HA is the acid

You want a pH of 5.02, and the pKa is 4.74, so the equation looks like:

5.02=4.74 + log[A-/HA]

You have 10mmol acetic acid, so the equation is:

5.02=4.74 + log[A-/10mmol acetic acid]

[A-/10]=1.904

Solve for A-
I got 19.04 mmol acetate.

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