## Chemistry: The Molecular Science (5th Edition)

Box number $IV$, $(D)$.
- Considering a strong acid being titrated; halfway to the equivalence point, the concentration of hydronium ions should be about half of the original. - Box number III (representing the beginning of the titration), has 16 $H_3O^+$ represented, and box number IV has 8. - So, the correct representation is box number $IV$.