A titration was performed on 50.0 mL of 0.250 M NaOH. After the
addition of 71.4 mL of HCL, the phenolphthalein indicator changed from
pink to colorless. What was the concentration of the HYDROCHLORIC
ACID?

At neutrality, Nacid = Nbase X Vbase/Vacid.

"The normality of a solution, represented by N, is the number of
equivalents of solute per liter of solution."  Chemical Principles,
fourth edition, by Dickerson, Gray, Darensbourg, and Darensbourg, The
Benjamin/Cummings Publishing Company, Inc., 1984, page 56

Because one mole of sodium hydroxide releases one mole of hydroxide
ions, and one mole of HCl releases one mole of hydrogen ions, the
molarity and normality are the same for both.

Therefore, the molarity of the HCl = (0.250M) (50.0 ml)/71.4 ml =
0.175M.

Sincerely,

Wonko