Question

HCl is a covalent compound. I do not understand why HCl cannot exist as an ionic compound with the combination of hydrogen ions and chloride ions. Is it a matter of electronegativity? I have once wondered if it is possible to obtain HCl crystals from hydrochloric acid, since I was told that HCl(g) ionizes in water to produce hydrogen and chloride ions. However, I have overlooked the fact that the so-called hydrogen ions exist as hydronium ions instead of pure hydrogen ions. Does anyone have some thoughts on the reason why HCl should be covalent, and whether it is possible to prepare HCl salt?Discuss.

Answer 1

HCl is a covalent compound that fully ionizes in water due to its strong acidity, forming hydronium and chloride ions. It cannot form an ionic solid or 'HCl salt' because its ions are only separated in solution, not in a solid crystalline structure.

Step-by-step explanation:

HCl, or hydrogen chloride, is a covalent compound because it consists of a polar covalent bond between the hydrogen and chlorine atoms. In its gaseous state, HCl is composed of discrete molecules that do not carry any charge. However, when HCl gas is dissolved in water, it reacts with water to form hydronium ions (H₃O⁺) and chloride ions (Cl⁻). This reaction is a demonstration of HCl's behavior as a strong acid, which dissociates completely in an aqueous solution.

Despite this dissociation, HCl does not form a salt crystal like NaCl because its ions only separate in solution, not in the solid state. It is the 100% ionization of HCl in water that characterizes it as a strong acid, and this ionization is facilitated by the interaction between the molecules of HCl and water, not by the formation of ionic bonds in the solid state. The production of hydronium ions in solution contributes to HCl's ability to conduct electricity in water, making its aqueous solution a good conductor, yet does not yield a typical ionic solid that could be crystallized into HCl salt.