Problem: A 26.00-mL sample of an unknown HClO4 solution requires titration with 21.92 mL of 0.2100 M NaOH to reach the equivalence point. What is the concentration of the unknown HClO4 solution? The neutralization reaction is: HClO4(aq) + NaOH(aq) → H2O(l) + NaClO4(aq)

FREE Expert Solution

Recall that at the equivalence point of a titration:

$\boxed{\mathbf{moles}\mathbf{ }\mathbf{acid}\mathbf{=}\mathbf{moles}\mathbf{ }\mathbf{base}}$

Also, recall that moles = molarity × volume. 

This means:

$\boxed{{\left(\mathbf{MV}\right)}_{\mathbf{acid}}\mathbf{=}{\left(\mathbf{MV}\right)}_{\mathbf{base}}}$

Solving for M_acid:

${\mathbf{M}}_{\mathbf{acid}}\left(\mathbf{26}\mathbf{.}\mathbf{00}\mathbf{ }\mathbf{mL}\right)\mathbf{=}\left(\mathbf{0}\mathbf{.}\mathbf{2100}\mathbf{ }\mathbf{M}\mathbf{\hspace{0.17em}}\mathbf{NaOH}\right)\left(\mathbf{21}\mathbf{.}\mathbf{92}\mathbf{ }\mathbf{mL}\right)$