Chemistry Buffer

Question

Which of the following acids would be most suitable for preparing a buffer of pH =3.10: hydrogen peroxide, propanoic acid, or cyanoacetic acid? Explain?

Answer 1

To prepare an effective buffer, you should generally choose an acid that has a pKa within 1 of the desired pH. Since we want a buffer of pH 3.10, we should choose a weak acid with a pKa in the range of 2.10 - 4.10.

Looking up the pKa's of the options provided, we find that cyanoacetic acid has a pKa ~ 2.5, whereas the others have much higher pKa values.

So, cyanoacetic acid would be your best choice.