Which of the following oxohalogen acids is the strongest acid?

Oxohalogen acids are acids that contain halogens bonded to oxygen, forming structures like HClO, HClO₂, HClO₃, and HClO₄. The acid strength of these compounds depends on the number of oxygen atoms attached to the halogen. The more oxygen atoms bonded to the central halogen atom, the stronger the acid. This is because additional electronegative oxygen atoms stabilize the negative charge on the conjugate base through electron delocalization, increasing acid strength.

Among the given acids, HClO₄ (perchloric acid) has four oxygen atoms attached to chlorine. The negative charge after dissociation is highly delocalized over the oxygen atoms, making the conjugate base very stable. This high stability results in extremely strong acidity, making HClO₄ the strongest acid among the chlorine oxoacids listed.

The acid strength trend for chlorine oxoacids is:

HClO < HClO₂ < HClO₃ < HClO₄

HClO (hypochlorous acid) is the weakest because it has only one oxygen atom bonded to chlorine, providing minimal stabilization for the conjugate base. HClO₂ (chlorous acid) and HClO₃ (chloric acid) have intermediate strengths due to increasing numbers of oxygen atoms. HClO₄ is a strong acid that completely dissociates in aqueous solutions, commonly used in laboratories and industry for strong acid reactions.

Understanding oxohalogen acids and their relative acid strengths is important in inorganic chemistry to predict reactivity, chemical behavior, and applications in oxidation reactions. It also demonstrates how electronegative atoms like oxygen influence acid strength through conjugate base stabilization.

In summary, HClO₄ is the strongest oxohalogen acid because the four oxygen atoms effectively stabilize the negative charge after dissociation, making it a very strong and fully dissociating acid in aqueous solutions.