To be honest, this looks like an insanely difficult problem for students that were not even shown HH equation. Especially if you are asked to use triprotic weak acid.
I am baffled, I have no idea how to help you, especially when the question is so incomplete. What does it mean "amount of the buffer" - volume of the solution? Number of moles of the substances used to prepare the buffer?
Citric acid has three relatively close dissociation steps. In general I would aim for a pH=pKa2 buffer, as the buffering effects of the pKa1 and pKa3 woudl help keeping the pH at bay after the strong acid/base was added, but if you are told to use citric acid and monosodium citrate (or is it something else?) you may be forced to use pH=pKa1.
I used the H-H equation after receiving info that the pka and pH in buffer solutions must be equal.
Yes, that will guarantee the maximum
buffer capacity.
Making the two equal, I calculated that the concentration of acid divided by the concentration of its conjugate base must equal 1. How can I do this step in the lab? How do I make the ratio equal to 1?
You have to assume concentration of one of them to be something and calculate how much of the other to add.
For what it is worth - while I know how to approach this problem to get an "exact" solution, it would require solving a set of fifth degree polynomials. Not something you want to try at home. The best approach I can think of is to download the
Buffer Maker (there is a 30 days free trial), learn how to use it, and play with numbers to see what can be done.