Twenty-seven milliliters of an acid with an unknown concentration are titrated with a base that has a concentration of 0.55 M. The indicator changed color when 12.5 milliliters of base were added. What is the concentration of the unknown acid?

Twenty-seven milliliters of an acid with an unknown concentration are

1.	Twenty-seven milliliters of an acid with an unknown concentration are titrated with a base that has a concentration of 0.55 M. The indicator changed color when 12.5 milliliters of base were added. What is the concentration of the unknown acid?
Answer» How the HELL do I KNOW that?