Question

How would I find the concentration of an unknown acid if I have a Ka value of 3.98x10^-5?

Answer 1

Hmmm. You have to know more than that.

Answer 2

sorry I forgot to add the rest. I also have the concentration of NaOH which is 1.0 M, pKa is 4.4, and the volume of the acid is 25 mL

Answer 3

You should type the problem from scratch. You also need to know the volume of the NaOH. Then
mols NaOH = M x L = ?
mols acid (if monoprotic) = mols NaOH
Then M acid = mols acid/L acid.