A 20.0 mL sample of an aqueous HClO3 solution is titrated with a 0.0275 M KOH solution. The equivalence point is reached with 28.5 mL of the base. The pH of the HClO3 solution, before titration, is
From the titration data you determine the M HClO3.
mL HClO3 x M HClO3 = mL NaOH x M NaOH.
Then given the HClO3 concn,
(H^+) = (HClO3) and
pH = -log(H+)