Chapter 15 homework

I am having trouble with #5. I assumed the answer to be Cu and Pb because all of the compounds listed have the same number of ions. The Cu and Pb have the smallest Ksp value but that answer is wrong.

Acid Base HW Q 19

I have been failing at this question for the past hour...

What is the pH at the equivalence point in

the titration of 20.0 mL of 0.200 M HA with

0.200 MNaOH? The Ka for HA is 5.04×10−6.

I know that at equilibrium there should be equal moles of acid and base. I also know that you have to use a "Kb" equation at equilibrium because the hasselhoff equation doesnt work, which is what i wrote down in my notes. Unfortunately, I can't figure out exactly what to do...