Question

Which of the following is the strongest acid?
(A) $Cl{{O}_{3}}\left( OH \right)$
(B) $Cl{{O}_{2}}\left( OH \right)$
(C) $SO{{\left( OH \right)}_{2}}$
(D) $S{{O}_{2}}{{\left( OH \right)}_{2}}$

Answer 1

Hint: Here, among all of the four given choices; any three will be less acidic than one will be more acidic in nature. The study of conjugate bases and its relationship with the acidic nature will help us solve this illustration.

Complete answer:
Let us know about what we mean by acids and then answer the given question;
The basic definition of acid is its intensity to give ${{H}^{+}}$ ions in the solution. Considering this statement let’s see if we can answer the given question.
Option (A)- $Cl{{O}_{3}}\left( OH \right)$
Here, chlorine has the highest oxidation number i.e. +7 and the conjugate base i.e. $Cl{{O}_{4}}^{-}$ has maximum delocalisation resulting itself into the weakest base.
The molecule has the maximum number of electronegative oxygen atoms which will pull electrons towards itself in the O-H bond, resulting in easy formation of ${{H}^{+}}$ ions. This will result in the stronger acid.
Thus, perchloric acid i.e. $HCl{{O}_{4}}$ will be the strongest acid among all of the given acids.

Therefore, option (A) is correct.

Note:
Do note that in the given question though all the molecules are written in different forms which may signify basic nature to many students but intelligently all are acids. Do not get confused.
Also, note that when the conjugate base is weak, the acid is stronger; and vice versa is also true.