Calculate the pH at the stoichiometric point of a titration of 25.0 mL of 0.120 M benzoic acid with 0.0230 M NaOH

1 answer

Calculate mL NaOH needed to reach the equivalence point.
mLacid x Macid = mLNaOH x MNaOH

Let HBz = benzoic acid then
HBz + NaOH ==> NaBz + H2O

The pH at the equivalence point is determined by the hydrolysis of the salt, NaBz. The (NaBz) = molsNaBz/L = ?. I will call that z.

.......Bz^- + HOH --> HBz + OH^-
I......z...............0.....0
C......-x..............x.....x
E......z-x.............x.....x

Kb for Bz^- = (Kw/Ka for HBz) = (x)(x)/(z-x)
Substitute and solve for x = (OH^-) and convert that to pH.