Question

Of the following acids, the one that is strongest is:
A. $HBr{{O}_{4}}$
B. $HOCl$
C. $HN{{O}_{2}}$
D. ${{H}_{3}}P{{O}_{3}}$

Answer 1

Hint: In this question, we are given some acids and we have to find out the strongest acid. We can find out the correct answer on the basis of their oxidation state. We know higher is the oxidation number on the central atom of a molecule, more is their acidity. By comparing the oxidation states of the atom, we find out the strongest acid.

Complete Step by Step Solution:
We can give the answer to this question by comparing the oxidation state of the given acids.
Compounds which are electron – deficient have the tendency to accept the electrons. Thus, they are acidic in nature.

And the compounds in which the central atom is present in lower oxidation state can easily lose the electrons to achieve a higher oxidation state. Thus they act as a base.
We know as the oxidation state of the central atom increases, acidity increases.
So the strong acid is that which has the maximum value of oxidation number on the central atom.

Here Option A is $HBr{{O}_{4}}$ (Perbromic acid)
It is an oxy-acid of bromine which exhibits its maximum oxidation state of +7.
Here in Option B it is $HOCl$ (Hypochlorous acid)
In this molecule, the oxidation state of Cl is +1
In Option C there is $HN{{O}_{2}}$ (Nitrous acid)
In this molecule, the oxidation state of N is +3
In Option D there is ${{H}_{3}}P{{O}_{3}}$ (Phosphorous acid)
In this molecule, the oxidation state of P is +3.
So by comparing all the oxidation states, we find that the Br possesses a higher oxidation state of +7. So we conclude that $HBr{{O}_{4}}$ is the strongest acid.
Thus, Option (A) is correct.

Note: Oxidation number is the total charge which is shown by a molecule or an ion, which is caused due to the gain or loss of electrons. As the oxidation state of a molecule increases, the charge density of that atom also increases, then such an atom strongly pulls the electron density towards itself and it becomes more acidic.