Problem: The pH of a solution prepared by mixing 50.0 mL of 0.125 M KOH and 50.0 mL of 0.125 M HCl is?

KOH + HCl → KCl + H₂O

strong   strong 

base       acid

Recall that moles = molarity × volume. 

Since:

• molarity KOH = molarity HCl
• volume KOH = volume HCl

Then:

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

This means: