Question

The addition of HCl will not suppress the ionization of:
(A) Acetic Acid
(B) Sulphuric Acid
(C) $ H_2S $
(D) Benzoic Acid

Answer 1

Hint: Electrolytes dissociate into positively charged (Cations) or negatively charged ions (Anions) in presence of electric current and these ions are responsible for conduction. For example, Acids, bases and salts. Some Electrolytes are strong (100% dissociation) while others are weak(less than 100% dissociation).

Complete answer:
In order to answer the question we need to have the knowledge of common ion effects. Common ion effect is the suppression in dissociation of a weak electrolyte (or decrease in degree of dissociation) in presence of a strong electrolyte both having a common ion.
Example-Consider the case of $ HCN $ (weak acid) and $ KCN $ (strong electrolyte)
 $ HCN \rightleftharpoons {H^ + } + C{N^ - } - - - - (1) $
 $ KCN\xrightarrow{{100\% dissociation}}{K^ + } + C{N^ - } - - - - (2) $
 $ HCN $ is already a weak acid and does not dissociate completely. As per the common ion effect dissociation of $ HCN $ is reduced when we add $ KCN $ to it since $ KCN $ produces $ C{N^ - } $ ions and the concentration of ions in solution increases to a level that to maintain the Equilibrium the reaction(1) will shift in the Backward direction reducing the dissociation of $ HCN $ even further and thus the production of $ {H^ + } $ also decreases. [Le-Chatelier’s principle].
In the given question we are adding $ HCl $ that dissociates as-
 $ HCl \to {H^ + } + C{l^ - } $
In order to find the correct answer we look at the dissociation of all the given options-
(A) $ C{H_3}COOH \rightleftharpoons C{H_3}CO{O^ - } + {H^ + } $ [Acetic Acid]
(B) $ {H_2}S{O_4} \to 2{H^ + } + S{O_4}^{2 - } $ [Sulphuric Acid]
(C) $ {H_2}S \rightleftharpoons 2{H^ + } + {S^{2 - }} $ [Hydrogen sulphide]
(D) $ {C_6}{H_5}COOH \rightleftharpoons {C_6}{H_5}CO{O^ - } + {H^ + } $ [Benzoic Acid]
In case of Options (A), (C) and (D) the dissociation or ionization is reduced as a result of common ion effect since all of them are weak in nature as compared to $ HCl $ which is strong acid. However only Sulphuric acid is the one that is a strong electrolyte and hence the ionization of Sulphuric acid will not decrease in this case. In Fact it increases the concentration of $ {H^ + } $ ions.
Therefore, Option (B) Sulphuric acid is correct.

Note:
 It is a very interesting fact that the Common ion effect is useful even in everyday life and has large industrial applications. It is highly useful in Water treatment, Regulation of buffer, Purification of salts, Qualitative analysis, salting out of soap, calculation of Solubility product and Manufacture of Sodium bicarbonate.