Question

A solution of NaOH with pH 13.68 requires 35.00 mL of 0.128 M HClO_4_ to reach the equivalence point. How do you calculate [Na^+^] and [ClO_4_^-^] at the aquicalence point? (volumes are additive)

Answer 1

We've been here before. What's the problem? You have M NaOH (from the pH = 13.68), you have mL HClO4 and you have M HClO4. There is only one unknown in
mL NaOH x M NaOH = mL HClO4 x M HClO4.