Question

# Assertion:$pH$ value of $HCl$ solution is less than that of acetic acid of the same concentration.Reason: In equimolar solution, the number of titratable protons present in $HCl$ is less than that present in acetic acid. A.Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.B.Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion. C.Assertion is correct but reason is incorrectD.Both Assertion and Reason are incorrect.

Hint: The acid which dissociates (ionization) completely in the aqueous solution is called strong acid and the acid which does not dissociate completely in the aqueous solution is called weak acid.

-The given acids in the question are hydrochloric acid ($HCl$) and acetic acid ($C{{H}_{3}}COOH$)
-$HCl$ is a strong acid which dissociates (ionization) completely in the aqueous solution.
-$C{{H}_{3}}COOH$ is a weak acid because it does not dissociate completely in the aqueous solution.
-Now, coming to the given assertion, as $HCl$ is a strong acid the $pH$ of the solution is less than the $pH$ of acetic acid (weak acid) of the same concentration.
-The assertion statement is correct.
-Now coming to Reason, as $HCl$ is strong means it will completely dissociate and release maximum number of hydrogen ions into the solution.
-But $C{{H}_{3}}COOH$ is a weak acid, it does not release all the hydrogen ions into the solution.
-So, the number of titratable hydrogen ions are high in case of $HCl$ when compared to $C{{H}_{3}}COOH$ of the same concentration.
-So, the Reason is wrong and not a suitable explanation for Assertion.

So, the correct option is C. Assertion is correct but reason is incorrect.

Note:
Don’t be confused with the words dissociation and ionization, both are the same. Dissociation means the acid or base is going to convert into ions. The dissociation of covalent compounds is also called ionization.