Determine the volume in mL of 0.470 M NaOH(aq) needed to reach halfway to the equivalence (stoichiometric) poi

Question

Determine the volume in mL of 0.470 M NaOH(aq) needed to reach halfway to the equivalence (stoichiometric) point in the titration of 44.7 mL of 0.619 M benzoic acid(aq).

Ka = 6.5 x 10-5.

Is there where you use pH = pKa?

I'm not sure how that fits into the halfway pt equation?

Answer 1

I didn't look at the solution as a buffer solution. I used stoichiometry to determine the equivalence point like a normal titration.

.0447L *(.619mole/L) *(1mole NaOH/1mole Acid) *(moles/.47M) = 58.9mL needed for equivalence point.

What we want is the midway point or when have the acid is neutralized. So all we need to do is divide the equivalence volume by two.

58.9mL/2 = 29.4mL needed to reach midpoint.