[camptzak]

You have 10 mols of Na^+-OH

You have 5 mols of COOH.

The 5 mols of COOH react with 5 mols of Na^+-OH

You now have 5 mols of sodium carboxylate, 5 mols of H₂0, and 5 mols of Na^+-OH

what is the pH of this solution?

I figured you took the -log(^-OH) ion concentration and added it to the pKw of 7 to give your above 7 pH

but also the sodium carboxylate is weakly basic as well. Do you take the inverse log of all your sodium salts and add them to the pKw 7?

10NaOH + 5COOH 5NaCOO + 5H₂O + 5NaOH

[AWK]

_{COOH, NaCOO}
Such compounds are not exist.
For pH calculations you need concentrations of compounds.

[camptzak]

pKa+pKb = 14

so if you were able to find the pKb then you could find the pKa. assuming all the mols are actually mols per liter.

does the sodium carboxylate count towards pKb as well as unreacted sodium hydroxide?

[Borek]

Write RCOOH (where R stands for anything) and RCOONa and your equations will become acceptable.

Hint: Henderson-Hasselbalch equation. Calculate concentrations of both acid and conjugate base assuming reaction went to completion.