How do I determine the concentration of an unknown acid or base solution?

The concentration of an unknown acid solution can be determined by titration with a strong base of known volume and concentration.  

The concentration of an unknown base solution can be determined by titration with a strong acid of known volume and concentration. 

When the volume and concentration of the titrant is known, you can determine the unknown concentration by calculating the number of moles of the titrant required to reach the equivalence point of the titration.