Question

A 15.0 mL sample of an unknown HClO4 solution requires 47.3 mL of 0.103 M NaOH for complete neutralization. What was the concentration of the unknown HClO4 solution? The neutralization reaction is: HClO4(aq)+NaOH(aq)→H2O(l)+NaClO4(aq)

Answer 1

The balanced chemical equation for the reaction between HClO₄ and NaOH is given below.

HClO₄ (aq) + NaOH (aq) -------> H₂O (l) + NaClO₄ (aq)

As per the balanced stoichiometric equation,

1 mole HClO₄ = 1 mole NaOH

Mole(s) of NaOH added = (volume of NaOH in L)*(concentration of NaOH in mol/L) = (47.3 mL)*(1 L/1000 mL)*(0.103 mol/L) = 0.0048719 mole (1 M = 1 mol/L).

Therefore, mole(s) of HClO₄ neutralized = 0.0048719 mole.

Concentration of HClO₄ = (moles of HClO₄)/(volume of HClO₄ in L) = (0.0048719 mole)/[(15.0 mL)*(1 L/1000 mL)] = 0.32479 mol/L ≈ 0.325 M (ans).