Question

13. Consider the titration of hydrofluoric acid (HF) with NaOH.

When one-half of the hydrofluoric acid has been titrated (the half-equivalence point), the two species present at equal concentrations are _____ and _______

(Before, at, or after?) ____ the equivalence point, the only species present in significant concentrations are OH- and F-

(Before, at, or after?) ______ the equivalence point, the only species present in significant concentration is F-

Answer 1

At half equivalence point 50% HF is dissociated and leaving 50% HF and 50 % F-

HF ----> H⁺ + F^-
Therefore;
When one-half of the hydrofluoric acid has been titrated (the half-equivalence point),
the two species present at equal concentrations are _HF _ and ___F-__

(Before, at, or after?) _After __ the equivalence point, the only species present in significant concentrations are OH- and F-

After equivalence point, there are excess amounts of OH- from NaOH and also completely ionized F- is present. Therefore, "After" is correct.

(Before, at, or after?) ___At___ the equivalence point, the only species present in significant concentration is F-

At equivalence point there is the completely ionized form of HF is present. That is F-.
Hence, "At" option is correct.