Question

Which of the following parent oxyacid does not have its hypo acid?
A. ${H_2}S{O_2}$
B. $HN{O_2}$
C. ${H_3}P{O_3}$
D. $HCl{O_3}$

Answer 1

Hypo acid is a weak acid that forms when chlorine dissolves in water, and itself partially dissociates, forming hypochlorite. The main element has the lower oxidation state than the present acid.

Complete step by step answer:
Hypohalous acid is an oxyacid that consists of a hydroxyl group which is single bonded to halogen. Some of the examples of this type of acid are hypofluorous acid, hypochlorous acid, hypobromous acid and hypoiodous acid. Basically the conjugate base is a hypohalite and they can be formed by reacting the corresponding diatomic halogen molecule with water. The reaction is as shown:
Where, X can be any halogen. ( ${F_2},C{l_2},B{r_2},{I_2}$ )
Here, as we know that the main element has a lower oxidation state than the present acid.
So,
HClO, $HCl{O_2}$ are hypo acid of $HCl{O_3}$
${H_3}P{O_2}$ Is hypo acid of ${H_3}P{O_3}$
HNO Is hypo acid of $HN{O_2}$
But ${H_2}S{O_2}$ doesn’t have hypo acid.

Hence, Option A is correct.

Note:
The strongest acid is perchloric acid and the weakest acid is hypochlorous acid. The only difference between these acids is the number of oxygen bonded to chlorine. As the number of oxygen increases, the acid strength also increases and hence the electronegativity increases.