Question

identify the weak acid(s). there may be more than one.

hclo4

h3po4

hi

hf

hcl

Explanation:

• \(HClO_4\) (perchloric acid) is a strong acid as it completely dissociates in water.
• \(H_3PO_4\) (phosphoric acid) is a weak acid. It has a relatively small \(K_a\) value and only partially dissociates in water (\(H_3PO_4

ightleftharpoons H^++H_2PO_4^-\), \(H_2PO_4^-
ightleftharpoons H^++HPO_4^{2 -}\), \(HPO_4^{2 -}
ightleftharpoons H^++PO_4^{3 -}\), with the first dissociation being the main one and all being partial).

• \(HI\) (hydroiodic acid) is a strong acid. The \(H - I\) bond is weak, and \(HI\) completely dissociates in water (\(HI

ightarrow H^++I^-\)).

• \(HF\) (hydrofluoric acid) is a weak acid. Due to the strong \(H - F\) bond (because of the small size of \(F\) atom and high electronegativity), \(HF\) only partially dissociates in water (\(HF

ightleftharpoons H^++F^-\)).

• \(HCl\) (hydrochloric acid) is a strong acid. It completely dissociates in water (\(HCl

ightarrow H^++Cl^-\)).

Answer:

\(H_3PO_4\), \(HF\)