Question

Water on reaction with hydrochloric acid forms?
(A) Hydronium ion and chloride ion
(B) Hydrogen and chlorine
(C) No reaction
(D) Hydrogen and chloride ion

Answer 1

Hint: water is chemically neutral; it reacts with both acid and base.
Strong acid is a strong electrolyte it completely dissociates in its constitutive ion in aqueous solution.

Complete answer:
Addition of hydrochloric acid into water is a highly exothermic process. Hydrochloric acid is a strong acid it completely ionizes into hydrogen ion and chloride ion in the water solution. In the presence of $\text{HCl}\,$dissociation of water molecules is suppressed, so hydrogen ions bind with water molecules to form hydronium ions. Bond dissociation is an endothermic process while bond formation is an exothermic process. So, energy release in the formation of hydronium ion utilises in the bond dissociation of hydrochloric acid. As a result acid is completely dissociated in the aqueous solution. These reactions are represented blow –
                                                       \[\begin{matrix}
  \text{HCl}\,\to \,\,{{\text{H}}^{\text{+}}}\,\text{+}\,\,\text{C}{{\text{l}}^{\text{-}}} \\
  {{\text{H}}_{\text{2}}}\text{O}\,\,\text{+}\,\,{{\text{H}}^{\text{+}}}\,\,\rightleftharpoons \,\,{{\text{H}}_{\text{3}}}{{\text{O}}^{\text{+}}}\,\text{+}\,\,\text{C}{{\text{l}}^{\text{-}}} \\
\end{matrix}\]

So overall reaction is $\text{HCl}\,\,\text{+}\,\,{{\text{H}}_{\text{2}}}\text{O}\,\,\,\to \,\,{{\text{H}}_{\text{3}}}{{\text{O}}^{\text{3+}}}\,\text{+}\,\,\text{C}{{\text{l}}^{\text{-}}}$

Additional information:
Strong electrolyte – those ionic conductors which are completely ionized in aqueous solution are called strong electrolyte. For e.g. ${{\text{H}}_{\text{2}}}\text{S}{{\text{O}}_{\text{4}}}$and$\text{HCl}$. For strong electrolyte the value of degree of ionization is 100% i.e. $\text{i}\,\,\text{=}\,\text{1}$

Note \[{{\text{H}}_{\text{3}}}{{\text{O}}^{+}}\]this is the aecidium ion also known as hydronium ion. It is the combined form of \[{{\text{H}}_{\text{2}}}\text{O}\] molecule and\[\,{{\text{H}}^{\text{+}}}\]ion.
Since water is a very weak electrolyte, ionization of water molecules is an endothermic process. Increase in temperature increases to\[\,{{\text{H}}^{\text{+}}}\]and $\text{O}{{\text{H}}^{\text{-}}}$concentration in the solution.