Based on the entries in the following table, which element is most commonly bonded to the acidic hydrogen? table some weak acids in water at 25 ∘c

The Correct is C₆H₅O⁻ : It is the most commonly bonded to the acidic hydrogen, and O2 is the most element bonded to the acidic hydrogen.

The explanation:

According to the table below we can see that the Ka (the acid dissociation constant) for the Phenol is the smallest one.

when the Ka expression for this chemical reaction:

C₆H₅OH (aq) ⇄ C₆H₅O⁻ (aq) + H⁺ (aq)

is

Ka = [C₆H₅O⁻] · [H⁺] / [C₆H₅OH]

So, the water solution of the phenol has a very low equilibrium concentration of H ions [H+], So C₆H₅O⁻ is the element which most commonly bonded to the acidic hydrogen.