Question

Name the ion(s) when \[HCl\] dissociates in aqueous solution.
A. \[{{H}_{3}}{{O}^{+}}\]
B. \[C{{l}^{-}}\]
C. Both A and B
D. None of the above

Answer 1

Hint: \[HCl\], a covalent gas acts as a typical acid when it is dissolved in the aqueous solution. Hydrogen ions (\[{{H}^{+}}\]) in the aqueous solution are called hydronium ions (\[{{H}_{3}}{{O}^{+}}\]).
The other ion formed is a halide ion. Halides are the elements present in the Group-17 of the periodic table. These are fluorine, chlorine, bromine and iodine.

Complete step by step answer:
\[HCl\] being a covalent gas is a poor conductor of electricity because there are no free electrons or ions.
When dissolved in an aqueous solution, it dissociates into \[{{H}_{3}}{{O}^{+}}\] and \[C{{l}^{-}}\] ions.
The reaction is as follows:
\[HCl(aq)\text{ }+\text{ }{{H}_{2}}O(l)\text{ }\rightleftharpoons \text{ }{{H}_{3}}{{O}^{+}}(aq)+\text{ }C{{l}^{-}}(aq)\]
The solution turns blue litmus paper into red because of the presence of \[{{H}^{+}}\](aq) ions.
\[HCl\] is completely dissociated in water.
 So it is a strong acid. It has a higher value of dissociation constant.
Dissociation constant (\[{{K}_{a}}\]) \[\text{= }\dfrac{[{{H}_{3}}{{O}^{+}}(aq)]\text{ }[C{{l}^{-}}(aq)]}{[HCl(aq)]}\]
Acids are proton donors and bases are proton acceptors.
So, the correct option is C.

Additional information:
\[pH\] of a compound is the negative logarithm of the concentration of hydrogen ions in the compound.

Note: The strength of an acid is determined by the stability of the anion being formed when dissolved in an aqueous solution. \[HCl\] dissociates into \[{{H}_{3}}{{O}^{+}}\] and \[C{{l}^{-}}\] ions in the solution. Now, the larger the counter anion the acid will be stronger because a large sphere can balance negative charge better than a small sphere. For this reason, \[HCl\] is a strong acid.