Question

Which of the following is not a strong acid?
(A)- ${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$
(B)- ${\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}$
(C)- ${\text{HN}}{{\text{O}}_{\text{3}}}$
(D)- ${\text{HCl}}$

Answer 1

Hint: Species which removes proton or ${{\text{H}}^{\text{ + }}}$ ion easily from itself to the other species in the aqueous solution comes under the category of acids. And the pH value of acids always presents between 0 to 7.

Complete step by step answer:
 From the definition, it is clear that proton donating species are acids. So, acids that eagerly or easily donates protons or gets fully dissociated in the aqueous medium will come under the category of strong acids, and those acids that do not donate protons easily or only show partial dissociation will come under the category of weak acids.
-In the option (A) Sulfuric acid (${{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}}$) is given and in the aqueous form it fully dissociates in the hydrogen ion and sulfate ion in the following manner and comes under the category of strong acid.
\[{{\text{H}}_{\text{2}}}{\text{S}}{{\text{O}}_{\text{4}}} \to {\text{2}}{{\text{H}}^{\text{ + }}}{\text{ + SO}}_{\text{4}}^{{\text{2-}}}\]
-In the option (B) Acetic acid (${\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}}$) is given and in the aqueous form it partially dissociates in the hydrogen ion and acetate ion in the following manner and comes under the category of weak acid.
\[{\text{C}}{{\text{H}}_{\text{3}}}{\text{COOH}} \rightleftharpoons {{\text{H}}^{\text{ + }}}{\text{ + C}}{{\text{H}}_3}{\text{CO}}{{\text{O}}^{\text{ - }}}\]
-In the option (C) Nitric acid (${\text{HN}}{{\text{O}}_{\text{3}}}$) is given and in the aqueous form it fully dissociates in the hydrogen ion and nitrate ion in the following manner and comes under the category of strong acid.
\[{\text{HN}}{{\text{O}}_3} \to {{\text{H}}^{\text{ + }}}{\text{ + NO}}_3^ - \]
-Similarly in the option (D) Hydrochloric acid (${\text{HCl}}$) is given and in the aqueous form it fully dissociates in the hydrogen ion and chloride ion in the following manner and comes under the category of strong acid.
\[{\text{HCl}} \to {{\text{H}}^{\text{ + }}} + {\text{C}}{{\text{l}}^{\text{ - }}}\]
From the above discussion it is clear that Acetic acid is not a strong acid.
So, the correct answer is “Option B”.

Note: Here some of you may think that the higher the value of pH shows the highest strength of acidity, but this is not true. A lower value of pH shows the highest strength of an acid and as the value of pH increases acidity decreases and above 7 basicity increases.