HClO₄ is a strong acid and NaOH is a strong base. Therefore they completely dissociate in the solution.
NaOH + HClO₄ ---> NaClO₄ + H₂O
stoichiometry of acid to base is 1:1
amount of NaOH moles reacted - 0.0789 M / 1000 mL/L x 50.00 mL
= 0.00395 mol
Amount of HClO₄ moles reacted = 0.00395 mol
Molarity of HClO₄ is 0.111 M
Volume of HClO₄ l containing 0.111 mol - 1 L
Therefore volume of HClO₄ containing 0.00395 mol- 1/0.111 x 0.00395 = 0.0356 L
Volume of HClO₄ - 35.6 mL
