Question

How would you represent Hydrogen chloride and Hydrogen chloride acid by chemical formulae? Why do they differ?

Answer 1

• Hydrogen chloride gas in its aqueous solution forms hydrochloric acid.
• Hydrogen chloride gas can be represented as $\mathrm{HCl}$(g) where “g” represents its gaseous state and Hydrochloric acid can be represented as $\mathrm{HCl}\left(\mathrm{aq}\right)$ where “aq” represents that the gas is dissolved in water.
• Both Hydrogen chloride gas and Hydrochloric acid have the same chemical formula but they vary in their chemical properties.
• The difference in their chemical properties is due to the absence of ions in the gas and presence of ions in the aqueous solution of the gas.
• Hydrogen gas is a covalent compound and does not contain ions whereas Hydrochloric acid has Hydronium ion $\mathbf{\left(}{\mathbf{H}}_{\mathbf{3}}{\mathbf{O}}^{\mathbf{+}}\mathbf{\right)}$ and Chloride ion$\mathbf{\left(}{\mathbf{Cl}}^{\mathbf{-}}\mathbf{\right)}$.
• The Hydronium ions are responsible for the acid nature of Hydrochloric acid.