Question

The correct order of acid strength is
A. $HCl{O_4} < HCl{O_3} < HCl{O_2} < HClO$
B. $HCl{O_2} < HCl{O_3} < HCl{O_4} < HClO$
C. $HCl{O_4} < HClO < HCl{O_2} < HCl{O_3}$
D. $HClO < HCl{O_2} < HCl{O_3} < HCl{O_4}$

Answer 1

The tendency of any compound to accept electrons is called acidity of the compound and Acidic strength of oxoacids depend on
$1)$Electronegativity of central atom and
$2)$ Oxidation state of halogen.

Complete step by step solution:
All the given compounds are the oxoacids of halogens with different oxidation states.
Oxoacid - Oxoacids are a group of chemical compounds in which both oxygen and halogen atoms are attached to another chemical element M in a single molecule
In case of oxoacids, Hydrogen is always bonded to one of the oxygen. In a series of oxoacids with the increase in the number of oxygen bonded to the central atom, the oxidation number of the central atom also increases. As the oxidation state of the central atom increases, the strength of the acid increases significantly, its tendency to draw electrons in a bond toward itself increases.
When the central atom pulls electrons away from the oxygen, consequently making the oxygen more electronegative. Therefore, the bond becomes more polar, making it easier to form ions and thus increasing the strength of the acid.
We calculate oxidation number of central atom Cl for all of these four :
Hypohalous acids($HClO$) ($+ 1$ oxidation state),
Halous acids($HCl{O_2}$) ($+ 3$ oxidation state),
Halic acids($HCl{O_3}$) ($+ 5$ oxidation state)
Perhalic acids ($HCl{O_4}$) ($+ 7$ oxidation state)
So here oxidation number of $HCl{O_4}$ is higher and it is the strongest acid and can easily release ${H^{+{\text{ }}}}ion$
$HClO < HCl{O_2} < HCl{O_{3}} < HCl{O_4}$

**Hence, option (D) is correct.

Note: **
In general, if a more electronegative atom is attached to the H atom, it will try to pull all the shared pairs of electrons towards itself. This will result in H atom easily being released, and the compound becomes a strong acid.