How do you figure out an amount of a base (say NaOH) required to destroy a base buffer capacity?

Given: NaH2PO4 6.5g and Na2HPOa 8.0g per 355ml. I found The PH, which was asked, to be 7.22. Then when .01 mol of HCl was added, the PH was 7.17. I need help with how do I go about solving how much Sodium Hydroxide is it going to take to destroy the buffer? Thanks in advance.How do you figure out an amount of a base (say NaOH) required to destroy a base buffer capacity?
It is difficlt to quantify and standardize when we can say that a base buffer can be destroyed. Basically, more amounts of NaOH could destroy it, but if you want to be specific, you can use the Hendersson-Hasselbach Equation:





pOH = pkb + log([conjugate acid]/[base]). Plug in the values and you get the pOH change. Note: the conj acid and base are in terms of Concentration.