Question

Which of the following is(are) true when $\mathrm{HCl}$ (g) is passed through water? (i) It does not ionize in the solution as it is a covalent compound. (ii) It ionizes in the solution (iii) It gives both hydrogen and hydroxyl ions in the solution (iv) It forms hydronium ion in the solution due to the combination of hydrogen ion with a water molecule

• A. (i) only
• B. (iii) only
• C. (ii) and (iv)
• D. (iii) and (iv)

Answer 1

The correct option is C

(ii) and (iv)

Explanation for correct option:

C. (ii) and (iv)

Reaction of $\mathrm{HCl}$ with water:

• Hydrochloric acid is a strong acid, it will dissociate completely into ions in water.
• When Hydrochloric acid$\left(\mathrm{HCl}\right)$ reacts with water, it produces hydronium ion$\left({\mathrm{H}}_3{\mathrm{O}}^{+}\right)$ and chloride ions$\left({\mathrm{Cl}}^{-}\right)$.
• The chemical reaction can be depicted as:

$$\begin{gathered} \mathrm{HCl}\left(\mathrm{g}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)\to {\mathrm{H}}_3{\mathrm{O}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right) \\ (\mathrm{Hydrochloric}\mathrm{acid})\left(\mathrm{Water}\right)(\mathrm{Hydronium}\mathrm{ion})(\mathrm{Chloride}\mathrm{ion}) \end{gathered}$$

• The concentration of hydronium ions decreases when acid is diluted.

Thus, the statements that are true ii) It ionizes in the solution (iv) It forms hydronium ions in the solution due to the combination of hydrogen ions with a water molecule.

Explanation for incorrect options:

When hydrochloric acid reacts with water, it ionizes the solution and forms hydronium ions in the solution due to the combination of hydrogen ion with a water molecule. Thus options A, B, and D are incorrect.

Hence, the correct option is C i.e. (ii) and (iv).