is it necessary why is it not necessary to know the exact mass of the acid whoe ka is to be determined?

Question

why is it not necessary to know the exact concentration of the NaOH solution used?

Answer 1

It is necessary to know the exact masses of everything. To determine Ka, you must have a solution whose [HA] = [A-]. In other words, you must have the known concentration solution exactly half neutralized by the NaOH.