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Acid/Base

You want to make a 0.1M acetate buffer from 0.1M solutions of acetic acid and acetate. How many mL of acetic acid would you need per liter of solution (with the rest of the volume coming from the acetate solution) to generate a pH of 4.75? The pKa of acetic acid is 4.76

Solution Preview

The simple answer is that since the pH of the solution we want is SO CLOSE to the pka of acetic acid, that you'd use almost an equal volume of 0.1M acetate and 0.1M acetic acid. However, let's show how this works out through the use of the Henderson-Hasselbalch equation.

pH = pKa + log [salt]/[acid]

What we want to find out is the ratio of [salt] to [acid] to use to generate the solution.

What do we know?

We know the pH we want and we know the ...

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