Now calculate Kb the base dissociation constant for [C2H3O2-], acetate anion, for each of your trials from the concentrations of species at the equivalence point.

Question

Report 3 significant figures, e.g. 5.97E-10.

Answer 1

I don't have access to your data but I expect you need to utilize the OH^-/HAc values you found.
........Ac^- + HOH ==> HAc + OH^-
I.......C..............0.......0
C......-x.............x.........x
E......C-x.............x.........x

C under acetate is concn of the salt. I suspect you measured the pH of the solution, converted that to OH^- and plugged into Kb = (x)^2/C-x. That gives you an experimental value for Kb. You can compare that with the actual value by Kb = (Kw/Ka) = (1E-14/Ka for acetic acid) = 5.56E-10